The Palestine Liberation Organization leaders and fighters, who once provided everything from guns and security to social services and pension checks to their refugee supporters, are gone now, and Mohammed Ihsan sits in yet another temporary home on the outskirts of a war-shattered camp wondering where his family will go next.

Mohammed, a Palestinian schoolteacher who asked that his real name not be used for fear of retribution, is -- for the fourth time in his 43 years -- homeless. He, his wife and nine children were hurriedly squeezed into an apartment building run by the PLO in August at the height of the Israeli siege of Beirut. Now the Lebanese government has ordered them to leave the building.

"Where do we go next? Into the street? We cannot even find an apartment to rent," he said, thoroughly disheartened. "When we came to this building we didn't know they had not bought the land." By "they" he means the PLO, which put up the seven-story building years ago on public land that the Lebanese government now wants back.

"We expect every day to get worse," said Mohammed, sipping coffee at a table with several of his daughters and his polio-stricken son grouped around him. "We will never finish with our problems. They are eternal."

He first fled his home near Acre in 1948 in the first great diaspora of refugees from Palestine. Since then, he has lost three other homes in the two refugee camps of Sabra and Shatila here because of the internal strife within Lebanon and the Israeli invasion last summer.

His was one of 70 homeless refugee families from Shatila that the PLO piled into one of its buildings alongside the bomb-gutted Cite Sportif beside the camp.

Today, the government is trying to evict them all on the grounds that the PLO building was constructed illegally on state land. Twice told to leave within 10 days, the families have now received a reprieve until April -- thanks to the personal intervention of Prime Minister Shafiq Wazzan, who is emerging as a kind of "patron saint" and defender of the refugees in place of the PLO.

After living for years like privileged citizens of a state within a state protected by its own army, hundreds of thousands of Palestinian refugees like Mohammed now face a new era of uncertainty and insecurity on their own within Lebanon.

The expulsion of the PLO has exposed the refugees to the raw elements of Christian-dominated politics in a "New Lebanon" whose slogan seems to be, "Palestinians, go away."

"The situation is catastrophic," said one Palestinian intellectual surveying the political scene. "The only thing worse is the situation in the country as a whole."

Bearing the brunt of the turmoil are the 100,000 to 120,000 refugees holed up in and around the eight camps here and in the south, which were largely pulverized by Israeli bombs and shells during last summer's invasion.

Shatila, where the massacre of civilian refugees by Lebanese Christian militia units was centered in September, remains a scene of devastation and misery. Its 5,700 inhabitants appear to be gripped by a pervasive sense of uncertainty about the future. The nightmare of the massacre has receded, only to be replaced by new fears of arrest, harassment and expulsion at the hands of Lebanese security authorities.

"We are not tortured today by the Israelis but by the Lebanese Army," said one undercover PLO official, pleading for anonymity. "We are not afraid of the Israelis, but of the Lebanese. This is worse. They do it legally."

Bulldozers have cleared away the rubble, but no new homes have gone up. The main road into the camp is often flooded with raw sewage bubbling from ruptured underground mains. Women and children still come to take water from broke pipes sticking out of the ground or to wash their clothes in the mud puddles.

On one side, a mass grave of massacre victims is marked by black flags and the shredded remains of a wreath, around which were once written the defiant words: "Sharon: The massacre of Sabra and Shatila will only increase our determination to struggle for our rights."

Yet there is little sense of struggle here except the struggle simply to survive.

The clank of Lebanese Army personnel carriers coming at night to arrest those suspected of belonging to one of the eight PLO factions has become a chillingly common sound now, according to the refugees. The big difference from the earlier indiscriminate sweeps through the camps, they report, is that the Army now comes with a list of wanted persons, the names apparently extracted from detainees.

The government admits to holding slightly more than 1,000 detainees in its prisons, about half of them Palestinians, and denies the use of torture. PLO officials assert the number of detainees fluctuates between 2,000 and 2,500, and those released say torture, beatings and malnutrition are common.

Arrests are not the only problem.

In the three official camps serviced by the United Nations Relief and Works Agency (UNRWA) -- Shatila, Burj al Barajinah and Mar Elias, housing 16,800 refugees -- 418 homes have been demolished and 857 badly damaged. Outside the camps, the destruction was even worse. In Sabra, which is not an official camp, 312 homes were blown away and 625 damaged, while in the nearby Harat Hurayk neighborhood the numbers were 415 and 720, according to UNRWA calculations.

The lack of housing, the fear of arrest and the official harassment have had their effect. Tens of thousands of Palestinians already have left the country, and more are going each day.

Government leaders, from President Amin Gemayel on down, have made it clear that only the original refugees who fled Palestine in 1948 and are certified by UNRWA have a hope of staying on. Today, UNRWA-registered Palestinians number 238,667.

But there are many others. How many they total has never been clear. Estimates vary like a "political accordion," as one PLO official put it, between 400,000 and 500,000, including an estimated 100,000 who have acquired Lebanese nationality.

This would seem to indicate that somewhere between 60,000 and 160,000 Palestinians were here illegally, many of them refugees from the 1970 "Black September" showdown in Jordan between the PLO and the Jordanian Army.

Nayef Sarris, the UNRWA Palestinian official in charge of Shatila, estimated that 15,000 to 20,000 Palestinians among the roughly 60,000 once living in and around the four Beirut refugee camps already have left the country.

Those bearing passports from Syria, Jordan or other Arab countries are drifting back there, he said, but thousands of others reportedly are fleeing via East Berlin and the underground subway connecting it to West Berlin, where they are seeking political asylum.

Yet it is far from clear that even the 238,000 registered refugees are really welcome to stay any longer. In September the government leaked a plan to reduce their number to 50,000. It has given no official permission yet for the 71,000 UNRWA-counted homeless from the war to rebuild, and it is generally keeping the status of the refugees in doubt.

Much of this suspense stems from the fact that the PLO and the Lebanese government have yet to reckon with each other on an official basis since the withdrawal, although PLO Chairman Yasser Arafat has called repeatedly for the opening of talks.

Once a military power stronger than the Lebanese Army and authorized under the so-called Cairo agreement of 1969 to operate here as a state within a state, the PLO must now renegotiate its entire status here.

All of its vast social, economic and political infrastructure, built up during 13 years, has been uprooted in the capital and throughout the south. Only in the northern city of Tripoli and the eastern Bekaa Valley are PLO guerrillas present in any numbers, their organization and refugee camps still intact and functioning.

Shafiq Hout, the top PLO representative, with the status of an ambassador, now operates out of his apartment and deals with those Lebanese officials who will talk to him, principally Prime Minister Wazzan, mostly by telephone.

In an interview there, Hout admitted the PLO was in disarray and unable to help the refugees.

"Everything is upside down," he said. "The government is so sensitive that any getting together by Palestinian officials is looked upon as revolutionary action. People have to look after themselves now."

Hout said his main preoccupation was "the future of the civilians and refugee camps," which the government was refusing to discuss.

"Gemayel is in a very difficult position and this is his last headache," Hout said, referring to the continuing occupation of most of the country by Syrian and Israeli troops.

He was clearly distressed by the trend of events and by the government's general attitude toward the Palestinians.

"Without trying to be fair and just, they are just driving people to despair and hopelessness with the intention the Palestinians will find it impossible and leave," he said bitterly, adding quickly: "But there is no place to go."

Hout said that none of the PLO organizations -- the workers' and women's unions, the youth group, the Red Crescent Society (the Palestinian Red Cross), the SAMED workshops, the Wafa news agency -- was officially operating any longer and that 4,000 to 5,000 civilians had lost their jobs in war-destroyed Palestinian factories.

Camp residents say, however, that some of the SAMED workshops have quietly reopened and that the women's organization is operating unofficially to help families who have men in jail or with relatives killed in the massacre.

An emerging major problem is how to get pensions distributed to the families of the 25,000 to 30,000 dead in past wars, since it is almost impossible for PLO officials to go into the camps now, Hout said.

"If I send a man to distribute money, they would see this as revolutionary activity, stop it and arrest him," he explained.

Before leaving Beirut at the end of August, the PLO distributed advance benefit payments for three months. The crisis for Palestinian families in Lebanon that depend on these payments did not begin until December, when the advance money ran out.

Keeping up the payments has been complicated by the PLO's need to keep the master lists of beneficiaries safe from both the Israelis and the Christian militia, who could use them to trace all Palestinian families with members linked to the organization. The master lists were originally kept in Sidon; when the Israelis invaded southern Lebanon they were quickly moved to Beirut, then smuggled out to Damascus, where they remain today.

This has created a totally new hazard for the Palestinians in Lebanon. To collect any benefits now, they must make their way to Damascus, past a gantlet of Lebanese Forces roadblocks along the Beirut-to-Damascus highway at the town of Sofar.

Palestinians in Beirut charge that in recent weeks 40 to 50 Palestinian women trying to get to Damascus to collect benefits have been kidnaped at the roadblocks at Sofar.

New Palestinian refugees from Lebanon recently arrived in Syria, interviewed in camps outside Damascus, describe incidents of brutality by Christian militiamen at the roadblocks--young Palestinian men gunned down, old people shoved and abused, women forcibly taken away.

At the Spinna refugee camp south of Damascus, for example, an old Palestinian woman from Tyre told of one grim scene she witnessed a month ago as she and members of her family sought to pass at Sofar.

The woman told of a Palestinian girl in her late teens being ordered by the Lebanese Forces militiamen to take off her clothes and dance naked at the roadside. When she refused and shoved one militiaman away, she was shot dead and her family was forced to leave her body by the roadside.

Another delicate issue is the fate of the hospitals run by the Red Crescent Society in the Beirut camps. On Nov. 28, the Lebanese Army seized $250,000 worth of medical supplies from their joint depot on the grounds that customs duties had not been paid. Most of the supplies had been donated by the Italians and international relief agencies.

Then, in early December, security officials went to the hospitals to check the residence and work permits of every doctor and nurse, threatening to oust anyone not having them. Few Palestinians, even among the 1948 refugees, have work permits. Most doctors, while certified by the Red Crescent, do not have them either, giving the government a perfect pretext to close the hospitals.

"We are in a very sensitive situation with the government," said Um Walid, the Palestinian director of Akka Hospital. "I am afraid tomorrow I will read in the newspaper they the doctors cannot work."

The only PLO institution that seems to have survived -- if not intact, at least as a functioning body -- is the Research Center in downtown West Beirut, which has diplomatic status. The Israelis, who occupied it in their mid-September thrust into West Beirut, took away its 25,000-volume library and a million dollars in other materials, including electric appliances and furniture, according to Sabri Giriyis, the center's Palestinian director.

But Giriyis, an Israeli citizen who fled in 1970, said he had blocked the Lebanese Army from also occupying and searching the center in late September by arguing that it had diplomatic immunity.

"I behaved somewhat legalistically and toughly with them," he said. "We have a legal status since 1965, and nobody can abolish it except the president or prime minister."

Giriyis was relatively optimistic that many of the old PLO institutions, like the hospitals, social services and workshops, eventually would start up again.

"It's not that they will allow it, but they cannot stop it," he predicted. "The problems are solving themselves."

But he thought it unlikely that the PLO would ever have the freedom or status it enjoyed in Lebanon before the Israeli invasion.

Just what the government is prepared to grant the PLO is far from clear yet. President Gemayel has let it be known that there will be no new "Cairo agreement" giving the Palestinians special privileges and yielding Lebanese authority over the camps and even some areas of the country to the PLO.

PLO leaders seem to accept this, but they say they want firm guarantees for the safety of the civilians and camps. They hope to use the withdrawal of 5,000 to 10,000 guerrillas in the north and east of Lebanon as a bargaining chip in their eventual negotiations with the government.

"We have no illusions but that the PLO is militarily out in the 'New Lebanon,' " said an official of one of the PLO's Marxist groups who is lying low here. "What we want is real security and humanitarian treatment of civilians."

"We also want Beirut as a center for political and information activities," he added. "From any other Arab capital, we will not have what we had here. This means a comprehensive agreement, even if no formal accord."

Whether this will ever be possible, even in exchange for the withdrawal of the remaining guerrillas, seems highly doubtful. For there is every indication that "the good old days" for the PLO in Lebanon are finished forever and the future of the remaining Palestinian civilian population is very uncertain indeed.