"At 7:30 p.m., when the executions were to start, the murder squads lined up along the steps leading down to the dungeon with hammers, crowbars, pistols and guns," Apollo Lawoko recalled. "Then the names of the condemned were called out, one by one."

Lawoko is a rare survivor of a 196-day stay in deposed president Idi Amin's pink stucco State Research Bureau in the plush residential section of the captial.

"When the prisoner's name was called out, the guards would go and grab him," Lawoko said. "We were all in handcuffs already - we were in handcuffs 24 hours a day - but they would change the position when they called a man, putting them on in back, and then they would place a long rope with a loop around his neck.

"Then someone would drag him by the rope along the staircase going up to the ground floor, and people would be beating him on all parts of his body. Then his head would be beaten in. By the time he reached the top of the stairs, he was dead.."

"We could see all this," said the soft-spoken Lawoko, relating his story as if recalling a faraway dream. Now, director of broadcasting for Ugandan radio and television, his tortured hands and face still are badly scarred from knife wounds and burns, and he walks with a limp.

"In fact," he continued, "the guards made sure we saw these murders through the small grill in the door to our cell. It was a form of torture for us. The blood would flow back into our cell as our fellow prisoners were killed."

For two agonizing months, Lawoko said he watched 150 to 200 persons begin killed this way every night. It was in early 1977 at the height of Amin's purge of Acholi and Langi tribesmen and when Anglican Archbishop Janani Luwum was murdered.

At the end of April, Lawoko said, the killings on the blood-caked dungeon steps tapered off - to only about regularly until his trial and subsequent escape at the end of August.

If his calculations are even roughly correct, Lawoko watched more than 15,000 Ugandans, most of them fellow Acholi and Langi, clubbed and beaten to death on the steps of the dungeon over a five-month period.

Such was the magnitude of the nightmare at the height of Amin's eight-year reign of terror over Uganda. It well may have been the most brutal regime anywhere on the African continent in contemporary times.

As more becomes known about it from personal testimonies like Lawoko's, it appears likely that the rough estimate of 250,000 Ugandans murdered by Amin may well prove true, perhaps even conservative.

This would mean that at least one out of about every 57 Ugandans has been murdered in the past eight years. Virtually everyone still alive seems to known someone who was killed.

"After hearing a relative or friend has disappeared almost every day," said Richard Mulando, a Kampala taxicab owner, "our thinking changed. Something which should be tragic became commonplace. This was the process of making us into savages."

That such a massacre of humans took place in this lush, green country that Winston Churchill once called the "Pearl of Africa" seems totally incongruous. Kampala is perhaps East Africa's loveliest city, with trim English-style gardens, wide, clean boulevards and modern high-rise buildings nestled among seven hills.

Amin once hailed Adolf Hitler and told U.N. Secretary General Kurt Waldheim the Nazi leader had been "right to burn 6 million Jews" during World War II. Amin even wanted to build a monument to Hilter in Kampala, but embarrassed African leaders finally prevailed upon him to drop the idea.

Amin appeared to the outside world mostly as a jovial buffoon of enormous size and limited intelligence. Ugandans, however, knew him as a different man - a shrewd, ruthless and dangerously unpredicatble man who indulged himself in killing his victims.

"Many said that Amin did not participate in the killings," Lawoko said, "but I myself saw him doing so on three occasions while I was there at the Bureau prison."

Lawoko said Amin personally took part in interrogating, torturing and finally killing Archbishop Luwum in a room next to the one where he was waiting to be questioned. That was shortly after his own arrest in mid-February 1977 as a suspected Acholi plotter like the archbishop.

Another time in early March, Lawoko said he watched as newly arrived prisoners were gassed and then Amin and his aides came down into the dungeon wearing gas masks and clubbed a number of them to death.

"Amin was actually participating," he said. "He turned to us at one point [in the next cell] and told us to relax."

On the third occasion. Lawoko said, Amin helped his State Research Bureau lieutenants use sledgehammers to kill a number of arrested police officers. "They rarely wasted any bullets on us," he said.

Killing anyone even slightly suspect was one key to Aminhs unexpected lonevity as Uganda's president. Another was his success in terrorizing the entire nation into fearful silence by allowing his henchmen to arrest, torture and kill with impunity. In the end, no one trusted or spoke to anybody else.

"The golden rule was not to talk about anything, anywhere to anybody," explained Hudson Sembeguya, a Kampala factory owner. "Even in the house, we'd literally have to whisper because we didn't know who was who. With inflation, many people, even servants, gave information for money.")

The measure of the psychological effects this has had on Ugandans is only now beginning to be realized and assessed fully as they talk to each other for the first time in eight years about their private experiences and ordeals.

"The reconstruction of buildings and the civil service, that can easily be done," said Harriet Kagwa, secretary general of the Ugandan Red Cross. "But to repair the damage done to the thinking of our people is going to be a big problem. I wonder if it can be done."

Although the Acholi and Langi were singled out for special treatment, Amin struck anyone vaguely suspected of disloyalty. The only people spared were his own tiny Kawatribe, Nubians and Moslems - not much more than 5 percent of the total 13 million population.

"Those killed were mostly educated or wealthy people who were not Moslems," said Kagwa.

A government lawyer, who asked to remain anonymous, said, "It was a crime to be educated. It was a crime to be Christian. It was a crime to be wealthy. It was even a crime to be seen with a foreigner or to have a wife or girlfriend Amin or one of his thugs wanted."

Amin effectively turned Ugandan society upside down to put outsiders, minority Moslems and illiterates in charge of East Africa's most highly educated and Christian country.

The system he built to terrorize his nation into total submission was staffed primarily by his own Kakwa tribesmen, Rwandan, Palestinian and above all Nubain mercenaries and the dregs of Ugandan society.

"From the earliest years, the State Research Bureau was mostly Nubian," said Sembeguya, whose father was killed by Amin. "But it would take on the weaklings from other tribes, the thieves and tramps, and suddenly they were given a golden chance of driving a car full of gasoline, extorting money and picking up people."

Everyone knew a Bureau man a mile away. They went around "incognito" in flowered shirts, dark glasses and platform shoes and often drove Peugeots with specially numbered license plates.

The hub of Main's intelligence-gathering and "law enforcing" apparatus was the Research Bureau, which was directly under him and linked to the presidential residence by a tunnel. Amin's Nubian sidekick, Maj. Farouk Minawa, was the effective head and set the tone for the 2,000 full-time and 5,000 unofficial employes posted throughout the society. They were civil servants, office messengers, doctors and priests, street hawkers and sweepers.

"He was a very cool man," reflected one of his family acquaintances. "He bumped off people he had been drinking with every night, after saying good night to them."

Among those Minawa reportedly killed were his own wife and three daughters because as Bagandas, he suspected them of helping the invading Tanzanian and Ugandan forces.

"He took them to the State Research Bureau and said, 'You Bagandas are all treacherous.' The boys refused to touch them so he took out a pistol and killed them himself," the acquaintance said.

There were many other cogs inthe security system besides the Bureau, including: the 500-member public safety unit of the regular police; the military police at Makinde; the Army's military intelligence unit; the Anticorruption Squad run by Main's British aide, Bob Astles, and a special presidential intelligence office set up toward the end by ahighly paranoid Amin to watch all the others.

Together they employed an estimated 15,000 persons and covered every corner of Uganda.

The system was at once methodical and highly capricious. The State Research Bureau had highly detailed and computerized files on tens of thousands of Ugandans at home and abroad whose movements were traced systematically through phone taps, freelance informers and full-time agents.

A search of the files shows Amin even had spies in the death-row cells of the Bureau's dungeons so that the condemned did not dare talk to each other.

To add to the capriciousness, the lowliest soldier or intelligence agent had license to arrest or kill anyone he deemed "dangerous to peace and good order."

"Everything you have seen in Wild West movies was everyday life here: Someone bumping off the husband and publicly taking the wife or someone bumping you off and openly driving off with your car," Sembeguya said.

"Finding a dead body was not something to talk about any more. In fact, you could hardly take a walk in Kampala without somebody saying. 'Oh, there's a body.'"

Sembeguya's sister, Lydia, explained: "I know a man who had a coffee-curing factory and the State Research boys extorted at least 300,000 shillings ($37,500) from him and still killed him. They wanted the man dead but they wanted his money as well and this happened in so many cases."

Another resident told how the International Hotel used to have an excellent rooftop nighclub. "One of the reasons it was moved from the top to the basement was that the State Research boys used to throw girls overboard or if they wanted to dance with a gril they would just toss the boy she was dancing with over."

Soldiers were apparently not much better.

"If a soldier wanted something, he just look it," recalled George Lukweya, a Kampala businessman. "He would come right into your house and if you didn't give it to him you would be killed."

Others told how they had seen a car stall in front of a military vehicle. The soliders got out, shot the occupants and then drove off.

Lukweya, an Acholi businessman who was picked up by the Bureau in January, told just how bad things were in the underground prison at the end of Amin's rule. He was thrown in a 10-by-12 foot room with 33 other people. They got two meals a week and had to drink each other's urine for water and took turns standing, sitting and sleeping.

After he was taken to be interviewed by Minawa, he was convinced he was "already a dead man."

"I went back to my cell, prayed to God and slept. I stayed 13 days without food and water. People died all the time . . . and they killed every day. They would pick out four or five people and kill them with hammers."

By the time he got out for unknown reasons, 34 of his fellow-inmates had the bodies in a corner. Tney wouldn't take them away. They would be there for a week and the smell was horrible."

Ugandans lived through Amin's hell in a dozen different ways. At least 120,000 fled to Kenya. Tanzania, Europe and America. The vast majority, however, could not afford to flee. Most Ugandans just lowered their heads, tightened their belts and did everything possible to avoid being noticed.

Beatrice Sembeguya explained that following her husband's murder, "We felt we had to stay as inconspicuous as possible. That was the key to survive in Uganda."

"What a lot of us did to survive was to play the fool," said one civil servant. "In fact, during these eight years some of us hardly did any useful . . . It was just sheer luck we made it, no magic or skill."

It came to the point where no Ugandan could trust a relative, friend or neighbor. "I had no happiness at all," said the Red Cross' Kagwa. "I couldn't go to my friends because I didn't know if they were with me or on the other side. I had nobody to trust any longer. Many of us began to find ourselves very isolated. We'd just fo from work to our homes, have dinner and go to sleep."

By the end, nobody even asked questions.

"We reached a stage where we did not dare ask why people were picked up," said the government lawyer. "We became insensitive. We would try to help the family who had lost a husband, son or other relative, but that was all.

"We stopped asking why a long time ago." CAPTION: Picture 1, IDI AMIN . .. shrewd, ruthless, unpredictable; Picture 2, 1975 photo shows Ugandan businessmen accused of overcharging and hoarding being flogged at Wobulenzi. AP