A rare public lecture here two weeks ago on the AIDS epidemic packed a large auditorium so tightly that the crowd of nearly 1,000 -- professionals, students, men in military uniform, housewives and others -- spilled into the aisles and kept yelling for the Soviet doctor on the podium to speak up.

After the 1 1/2-hour talk, including an extensive question-and-answer period, the audience's curiosity seemed hardly satisfied.

"This disease has been known for a long time," said a middle-aged man, who had pushed through the crowd and grabbed the microphone, "but not here, unfortunately. We have only known about it for the last hour. That's why . . . all of us are scared."

Amid signs abroad of a mounting epidemic of the Acquired Immune Deficiency Syndrome, fears about the disease in the Soviet Union -- as it affects Soviets and foreigners -- appear to be on the rise.

Although a Soviet doctor last week acknowledged that there were several cases of AIDS in the Soviet Union, Soviet officials still characterize the disease as a foreign problem, apparently to underline the stigma they attach to foreigners, especially westerners.

The lecturer and other official Soviet sources and press reports have gone to pains to keep a lid on the AIDS situation in the Soviet Union and other East Bloc countries. The lecturer, who was introduced as "Arkady" but not fully identified, said there were cases of Kaposi's sarcoma, a skin cancer that can be especially deadly in AIDS patients, in Moscow, but he knew of no registered cases of AIDS. Although Hungary and Poland have reported cases of the disease, the reports have never been mentioned in the popular Soviet press.

Two weeks ago, former health minister Boris Petrovsky told journalists in a press briefing that the Soviet Union had "no registered cases." But in an interview last week in the official newspaper Soviet Culture, V.M. Zhdanov, director of the Soviet Institute of Virology, said that there were some cases -- "fewer than on the fingers of a hand."

But western businessmen who import medical equipment used to test for AIDS estimate that the number of cases here could "number in the hundreds," one said.

In his presentation late last month at Moscow's Vishnevsky Institute of Surgery, the lecturer fanned the common Soviet impression that AIDS is a peculiarly western problem by detailing the spread of it through the United States, West Germany, France and other Western European countries.

Recent articles in the Soviet press have attributed the source of the AIDS epidemic to the Central Intelligence Agency, or to tribes in Central Africa.

Most articles in the Soviet press have described AIDS as an infectious disease most prevalent among homosexuals, drug addicts and prostitutes. But the lecturer stressed that the instances of AIDS among children and married people is also increasing.

In the Soviet Culture interview, Zhdanov blamed the outbreak of the AIDS virus abroad on the increased contact between people from different countries in the postwar period, and particularly since the 1960s. Since then, he said, "contacts have multiplied. That's why the opportunity of the disease has increased."

Near the end of his lecture last month, the doctor topped his list of preventive measures with a recommendation to avoid contact with foreigners and undesirable elements. He added that blood for transfusions should be drawn from women, who he said are less likely to be carriers of AIDS.

Immunization measures, he said, were not discussed in the articles available in the Soviet Union.

Although even western estimates of AIDS cases in the Soviet Union are minuscule when compared to the thousands who have been affected in the West, official Soviet sources still resort to whispers and denials when they discuss the AIDS situation here. One reason, western analysts say, is that Soviet officials are reluctant to acknowledge the presence of the groups most commonly affected by the disease -- particularly homosexuals and drug users.

Articles in the Soviet press appear to have increased suspicions against foreigners. A rash of official reports about AIDS before the International Youth Festival here last summer has given way to persistent but unproven rumors throughout Moscow that contacts between Soviets and foreigners during the July celebration have resulted in an outbreak of AIDS here.

Public concern about AIDS here was apparently touched off by a long article about AIDS entitled "Panic in the West," published in October in the Soviet weekly Literary Gazette. The article, written by Valentin Zapevalov, charged that the epidemic was triggered in the United States by the Pentagon and the CIA.

The effect on the Soviet public was strong. Several individuals interviewed at a bar frequented by homosexuals in central Moscow said they had read it and several people brought the article to the lecture last month. A Soviet official in Voronezh, 300 miles south of Moscow, recently asked an American visitor whether the allegations were true.

Interest in AIDS among Soviets, according to the crowd gathered for the lecture, is great. Advertised solely by word of mouth, it drew nearly 1,000 people, including about 150 men in military uniform.

Before he gave up the microphone, the audience member who voiced the fears of the crowd suggested that a Moscow newspaper publish some information to calm the excitement about the disease. In possible response, the Literary Gazette today published another article on AIDS, entitled "The Panic Continues." It said that throughout the world, an estimated 15,000 cases of AIDS have been identified. But, responding to a question about the possibility of an epidemic, the author wrote that "I think we can view the future with optimism."