When American tanks pushed through the gates of the Nazi concentration camp at Mauthausen in Austria on May 5, 1945, Simon Wiesenthal lay on his bunk, too weak to greet his liberators. He was 37 years old and 6 feet tall. But he weighed only 90 pounds and had been in and out of such camps for 4 1/2 years.

In the chaos and bewilderment of those first days, Wiesenthal was beaten up by a Polish "functionary" in the camp when he asked for documents that would eventually allow him to leave. When he went to the American camp directors to tell of the beating, a young officer told him: "We have a special branch for that. It's called war crimes."

It was the beginning of a second life for Simon Wiesenthal, a life that would transform a once-promising young Austro-Hungarian architect into a sort of Jewish James Bond-the most extraordinary freelance Nazi hunter of the postwar era who rarely left his tiny office and precious files but who, by talmudic scrutiny of tips and documents, would provide the key to tracking down some of contemporary history's worst murderers.

Wiesenthal is 70 now. Behind him lies his biggest case-his report in 1953 that Nazi extermination chief Adolf Eichmann was living in Buenos Aires, and his hardest case-the five-year search to find the Gestapo officer who arrested Anne Frank and her family in their hidden apartment in occupied Holland.

Mixed among them have been over 1,100 Nazi-era war criminals who have been brought to justice by Wiesenthal's painstakingly prepared dossiers and the occasional cooperation of several governments.

Today, he remains a driven man-his big, brown eyes alert with the excitement of the hunt and catch even after 34 years of morbid digging.

He is a man of considerable ego, proud of the testimonials and honorary degrees that line his sparse, three-room "documentation-center" offices here. He is most proud, however, of the Simon Wiesenthal Center for Holocaust Studies, which will be dedicated April 24 by the Yeshiva University in Los Angeles. "The honorary degrees will die with me, but this center will survive," he says.

Mostly, however, Wiesenthal is one-of-a-kind, a talkative, irreverent guide to the horrors and humanity that sprang from the Naziera and lingered in its aftermath. When he ends his work, an era will end because his lifetime spans those of the criminals and their victims. There is no other office like his, no one of similar reputation, no one with his personal links to justice officials in Germany and elsewhere, no way to transfer the impact of his name.

"This is also my tragedy," he says in heavily-accented English with a touch of bitterness. "Our office is the last in the world. My work may speak only for me, but in a way it speaks against the Jews because what was my duty was also the duty of thousands of others to do yet we had even to fight for money for our work with other Jewish organizations."

Though Israeli intelligence has also fingered Nazi war criminals in the past, Wiesenthal maintains "you can't really do this work from Israel because then it looks like Israeli propaganda." What he doesn't say is that there is no Wiesenthal there for people to come to with tips.

After the U.S. television series "Holocaust" was shown in West Germany and Austria in recent months, the center here received 400 letters and telephone calls with new tips on former Nazis, "more in three weeks than we normally would get in three years. Four hundred were from Germany and three from Austria." Though he lives and works in Vienna, Wiesenthal is harsh in his judgment of what he views as Austria's failure to come to grips with its enormous wartime participation in and acceptance of Nazism.

"Also, I'm not dividing the victims," he continues. "This was one of the biggest mistakes made on the side of the Jews. Since 1948 I have sought with Jewish leaders not to talk about 6 million Jewish dead, but rather about 11 million civilians dead, including 6 million Jews.

"This is our fault, that it in world opinion we reduced the problem to one between Nazis and Jews. Because of this we lost many friends who suffered with us, whose families share common graves. After the war, there was a possibility to make a brotherhood of victims and survivors against dictatorship. But the survivors were sometimes misrepresented after the war by people who were sitting in safe countries during the war and who gave priority to material restitution."

Not surprisingly, Wiesenthal has injected himself into the current West German debate about whether to lift the statute of limitations on war crimes of murder which would take effect at the end of this year. Wiesenthal opposed letting the statue come into force, arguing that nothing must stand in the way of bringing war criminals to justice until there is either a legal or "biological" solution, meaning that no ex-Nazi could live out his life in safety. Sentiment in the Bonn parliament is now generally in favor of extending the statute.

Money has always been a problem for Wiesenthal. His center, he says, costs about $120,000 a year to run. "That is peanuts for a Jewish organization," he says. Virtually all of it comes from a Wiesenthal foundation in Holland with a few thousand members, only 10 percent of them Jewish, and from individual tax-deductible donations from the U.S. through a New York office. There are also donations from the Jewish War Veterans and a Chicago federation.

He says he takes no salary but lives off royalties from his books and a pension from Germany. Two of his six office workers are volunteers.

Though he claims he is not much of a fund-raiser, Wiesenthal is, in fact, a master publicist, a robust and naturally attractive man whose record of accuracy brings comfort to newsmen and who frequently turns to newspapers to get infromation out when countries turn away from him.

In over 3,000 cases he has pursued, he has been sued for libel only three times. Two of those suits he won and the third, involving Austrian politician Friedrich Peter-who Wiesenthal says belonged to a wartime SS extermination brigade-is still underway.

Wiesenthal's story begins like that of millions of other Europeans and Jews caught in the unprecedented depravity of the kind of war Hitler launched. As a Jew, he was first confined to a ghetto and then to a concentration camp in Lemberg, which today is in the Soviet Ukraine but in 1941 was occupied Germany. He escaped, was caught, and then shipped as a laborer to camps at Plaszow and Gross-Rosen in Poland, then Buchenwald and finally Mauthausen, being moved steadily westward as Russian armies pushed into the Third Reich from the East.

In June 1944, he tried to commit suicide. Later, the notion "that we could be dead in 15 minutes or liberated in 30 minutes" kept him alive, along with an extra ration of soup daily from a kindly Pole-Edward Staneszewski- who befriended Wiesenthal in camp and probably saved his life. Wiesethal still writes to him today.

But when the U.S. Army's 65th Division tanks came to Mauthausen, Wiesenthal, Wiesenthal's life began to swerve from the rest.

The polish functionary who beat him, he says, was Kasimir Rusinek, who later became Warsaw's Minister of Culture. "If you can beat a skeleton," Wisenthal wondered, "what else could people have done?" He sat on the barracks stpes "feeling all alone. My mother had been killed in the Belzec concentration camp and I was convinced my wife lay under the rubble of Warsaw's ghetto. I had no home. Every stone in Poland meant tragedy. But the sight of prisoners and American officers working in the war-crimes branch for justice made me forget why I was here."

He started accompanying an American captain as a translator;and when they arrested their first six SS officers, he began to understand shock in victims and victimizers. "They did nothing. There was no resistance. They thought we would do to them what they had done to the Jews," he says.

Soon, the captain went back to the United States and Wiesenthal was so good that he was left on his own with a couple of military policement. Then shock came again. He was sent to arrest a local Nazi functionary in a small town. The two U.S. MPs stopped to talk to some girls and Wiesenthal, still weak, had to climb to the third floor apartment to make the arrest. The Nazi was curled in the corner, unresisting. But Wiesenthal was too weak to make it down the stairs and the Nazi official helped him down. "He, too, was paralysed, the same as we were."

Soon he was transferred to thr U.S. Office of Strategic Services and then to U.S. counter-intelligence. Then strange things happened. "During the day I would bring in a few Nazis and the next day some them were free. Why?" he asked. "Because my superiors would sleep with the wives and daughters who would come to plead for their men. Sometimes I would arrest the same people three times. Ii began to have quarrels over our obligations, so after a while I felt we had to tatke the matter in our own hands."

So, with "30 desperados," he left the Americans and built the "Jewish Documentation Center" in Linz, Austria, in December 1946. By then, he had found his wife, Cyla, a member fo the family of psychiatrist Sigmund Freud, who had survived via the underground in Krakow.

Wiesenthal quickly set up, correspondents in the displaced-persons camps in Germany, Austra and Italy that still contained some 200,000 Holocaust survivors. Within three months, he had a list of 1,000 places where war crimes were committed and thousands of witnesses by name. "We sent this to all the Allies. No one had this. This was totally new."

As the cold war began, however, and Germany became a prize rather than a smoldering ruin, interest in the Allied and Soviet world about prosecuting Nazis dwindled, though Wiesenthal's did not and his evidence was heavily used in the U.S.Zone trials. Eventually, though, his helpers drifted away and by 1954, he had to close his ecenter. He shipped all his files to the Israelis except one, the dosier on Adolf Eichmann.

At first the U.S. FBI, Wiesenthall said, did not believe his information of Eichmann's whereabouts. Nor did the leaders of the World Jewish Congress. The Israelis said nothing. But by 1959, the Israelis were involved and later that year Israeli agents found him where Wiesenthal said he was.

The Eichmann success brought fame to Wiesenthal and renewed interest elsewhere. His center reopened here, in Vienna's garment district, in 1961, newly called "Documentation Center."

New information and tips came. In 1966, a man showed up in the Vienna office who promised to disclose the whereabouts of Fritz Stangl, commandant of the Treblinka death camp, if Wiesenthal promised never to try and identify or track down the man standing before him and if he would also give $25,000. Wiesenthal objected. "What do you want, Stangl or morality?" the man asked. Wiesenthal signed a pledge on both conditions, but offering onl $7,000. In 1967, Stangl was arrested by Brazilian police. A few months later, a German notary showed up bearing Wiesenthal's signature and the money was paid to the anonymous informer. Nazis turning each othe in is, Wiesenthal siad, perhaps his greatest satisfaction.

The hunt for Stangl eventually led to the discovery of his deputy, Gustav Wagner, in Sao Paulo, Brazil, last year. He, too, is now in jail.

Wiesenthal's interest in the Anne Frank case was more profound. The play, "The Diar of Anne Frank," opened in Vienna in 1958 and it was picketed by bands of Austrian youths who said it was all a lie. Wiesenthal confronted them and they said the only way they would believe it was to find the man who arrested her. In 1963, after years of digging and checking, a man named Silberbaur, then an Austrian police officer, confessed that he had in fact arrested the Frank family on orders from higher authority.

To Wiesenthal, the Frank case must not be discredited because, in terms of its impact on people, "it is more important than the Nuremberg trials." He says he has Eichmann's memoirs and in them Eichmann says, "100 deaths is a catastrophe but 1 million is a statistic." Wiesenthal feels the samy way about the "Holocaust" television, that whatever its minor errors, its ability to reduce the horror to a scale that people can absorb is of crucial importance.

It is important not only for German or Austrian youth, but also for Americans who, in many universities he visits, show little or no real understanding of what happened in Europe, he says.

Looking back and ahead, Wiesenthal finds hope, bitterness and foolishness in the actions of people and governments.

He is not a believer in collective guilt, unwilling to tar all Germans, for example, with the Hitler brush. He gives a very high vote of confidence to today's West German youth and high marks to West German investigators in the three centers where war criminals are first looked into by the Bonn government in Ludwigsburg, Cologne and Dortmund.

That is not his view of Austria. "They are two nations with different characteristics," he says of Austria and Germany. "The Germans are an accurate peole. They get an order to kill and they kill. They get an order to make the research and they make the research." About 7,000 war criminals have been convicted in West Germany since 1949 with another 5,000 still under investigation.

But in Austria, he claims, "There is a sense of collective innoncence" even though he estimates there are about 250,000 former Nazis alive in Austria today. Wiesenthal and Austrian Chancellor Bruno Kreisky-a born Jew who dropped his religion as a young man are bitter enemies and Weisenthal charges that Kreisky keeps some of these former Nazis "kosher" by calling them liberals, a reference to right-wing parties here whose swing votes often are necessary to keep a government in power.

"In 10 years of Kreisky," Wiesenthal says, "there have been eight Nazi trials and six acquittals and no more trials since 1975."

Wiesenthal feels anti-semitism, at least in part, traveled from Austria to Germany. Hitler, who was an Austrian, did not invent it, he says, "In Germany, the Jews were intergrated. In Austria, they were not."

The population of Austria was only 8.5 percent of that of greater Germany, he says, "but Nazis from Austria are responsible for 50 percent of this crimes." Partly, this was because of "an accident of history. Not only was Hitler Austrian, but Eichmann came here as a 4-year old and the man SS chief Himmler ordered to oversee three notorious extermination camps in Poland-Odilo Globocnig-was Austrian. When he went east, henaturally took much of his staff with him. Sixy-five percent of the names on the Austrian war-criminals list are Slavic," Wiesenthal say, "people who probably felt they were not viewed as 100 percent Germans so they compensated by being 150 percent murderers."

Austria was invaded by the Germans and was declared an occupied country, which Wiesenthal feels has produced this feeling of collective innocense. Indeed, he says, many thousands of Austrians were killed.

"But there were 660,000 members of the Nazi party here, maybe 10 percent of the population, about the same proportionally as Germany. Is that an occupied contry?" he asks.

In West Germany, he says, "the prosecutors are doing a very good job. But you know that after 35 years, German justice is tired" of war-crime trials. Defense lawyers have learned the lessons of prolongation and intimidation form trials of the Baader-Meinhof terrorists. Still, he says the argument of German justice, that these must be conducted legally precisely because of the past, "must be accepted. Nothing is perfect in our world. We lost 11 million witnesses to crimes and 100,000 documents in the eastern communist countries are not available to us because for their own propaganda reasons they have no interest in seeing the west punish Nazi criminals."

Even for communist East Germany, which claims under Soviet rule to have purged all the Nazis, Wiesenthal claims there are still 1,000 active cards in his files.

Wiesenthal estimate that about 150,000 Germans committed war crimes and that 95 pecent of them survived the war. He estimates about 60,000 were brought to trial, though again he says figures from the east are unreliable. Many have died. He estimates 15,000 to 20,000 "murderers" are still free today and living in South America, Spain, the Near East, Germany and other countries.

On top of his personal list is Dr.Josef Mengele, the infamous "angel of death" SS doctor at Auschwitz, who Wiesenthal says is living in Paraguay. Next is gas chamber-builder Walter Rauff, who lives in Punta Arenas, Chile, Wiesenthal says.

Beyond them are thousands of non-Germans whose crimes Wiesenthal feels sometimes are even bigger. They are the collaborators in the Baltic, Ukraine and elswhere in the east who profited from pointing out the Jews to the Nazi occupiers who could not tell the difference in strange countries.

Many of them, he says, live today in the United States, Canada and Australia. There are now procedures against 300 in the United States, but he says there are really more than 3,000 cases thre. The U.S. Immigration and Naturalization Service is too small for all the work, he says, though relations are good. But in Canada, he says, there is not even a partner to speak with and so he works throught the Cannadian press.

"Could it happen again, even in the United States?" Wiesenthal is asked by American college audiences. "Yes, I answer. All you need is a government program of hatred and a crisis. If it happened in a civilization nation like Germany, which was a cultural superpower, it can happen anywhere. When I was a youngman in the 1920s, our answer to Hitler was to laugh and make jokes. How could a man with such crazy ideas succeed?"

"It was suck a little group. But you have groups 10 times bigger in the United States today, like the White Peoples' party. There are 85 extreme rightwing American organizations that wait for a crisis." In England, he sees a country with a crisis and a national-front movement with over 100,000 people.

"In West Germany, they always had good soldiers and bad politicians and they still have bad politicians." What he means, he says, is that Bonn was not cracking down hard enough on the tiny bands of neo-Nazis, the "one or two in a thousand who give West Germany a bad name before a world that doesn't want to believe the Germans have changed. I want to tell you the German youth today are working and serious; but after this catastrophe, we need to give them confidence because if you don't they will join the older generation who will tell them they are innocent but the world is agains them anyway."

In the corner of one room here, a young woman sits and enters cars in files about neo-Nazi activities all over the world. It is one part of Wiesenthal's work that he feels will survive him and can be carried on by his young aides.

In 1964, Wiesenthal once ansewered a newsman's question about what motivates him by relating a conversation he once had with another former inmate Mauthausen who had become a successfull jeweler.

"when we come to the other world and meet the millions tof jews who died in the camps," Wiesenthal told the man, "and they ask us, 'What have you done?' there will be many answers. You will say, 'I became a jeweler.' Others will say, 'I smuggled coffee or American cigarettes.' Another will say, 'I built houses.' But I will say, 'I did not forget you.'"

Today, slouched in an old easy chair in front of his cluttered deks, Wiesenthal says it is his daughter and three grandchildren in Israel who "provide the gasoline for my motor."

And what will remain form his work" "A warning to the murderers of tomorrow. Maybe they are already born today. But they must know what to expect, that nowhere in time or space will they be safe.

"To sit here at this deks and hear form Sao Paulo, Brazil,37 years after the crime and 8,000 miles away that a man cannot feel safe, that is warning. I am sure there will be both murderers and people like me who will go after them if governments do not do their job."