MOSCOW, SEPT. 22 -- This fall in Moscow is the season of the artists' return.

It began with the jubilant downtown opening of long-neglected works by the Russian-born Marc Chagall. Today, it spread to the city's edges, where a retrospective of Soviet abstract art, including works by prominent e'migre' artists, was unveiled on the first floor of a prefab apartment building.

The show at 100 Belayeva St., in the Brezhnev District's official exhibition hall, is just as historic as the dazzling display of Chagalls at the Pushkin Museum. Here, for the first time in an official setting, are gathered works of more than 100 modern Soviet artists, most of them "unofficial," many of them victims at one time of official scorn or worse.

But what is most surprising of all, even in these days of glasnost, is that 17 of the artists left this country -- some in disgust, some in despair. Their "return" this week is viewed as a sign of some relenting in the Soviet Union's official intolerance toward those who leave it.

According to organizers of the show, the works of only one e'migre' artist -- Oskar Rabin, who now lives in Paris -- were removed from the exhibit by local cultural officials during an inspection before the opening.

One of the works left untouched was a small figure by Ernst Neisvestny, a sculptor who became known around the world because of a public debate with Soviet leader Nikita Khrushchev in 1962. Khrushchev called Neisvestny's work fit only for the "walls of urinals," but after Khrushchev's death it was Neisvestny who was asked to design his tombstone in Novidevichy Cemetery. Neisvestny left the Soviet Union in 1976, around the time Novidevichy was closed to the public, in part because of the crowds attracted to Khrushchev's grave. (The cemetery was reopened last winter in another symbolic gesture of glasnost.)

Many of those who came to Belayeva Street today had already seen the artists' works -- at private studio showings, or among the city's private collections. Many of the artists make a living by selling their works abroad, and are better known in France or Germany than in the Soviet Union. The exhibit, put on by a newly formed group of artists called the Hermitage, will be shown in two stages. Today's was a display of works from the 1960s and the early 1970s. The second half of the show will display works produced since.

According to the organizers, the retrospective is in fact a beginning -- the start of a permanent collection for a soon-to-be-established Museum of Contemporary Art. No such museum exists now in Moscow, and its prospects are still nebulous since the Hermitage group, now numbering about 70 artists, has not yet found it a home. But the artists insist they will, noting that the museum was included in their charter when they registered with Soviet authorities last December.

Several of the artists shown here are survivors of the "unofficial" Moscow art show of 1974, which was broken up by plainclothesmen and crushed by bulldozers at a site not far from Belayeva Street. Some said today that even a year ago they never thought such an exhibit could take place under official auspices.

But over the past year, a few art exhibits have taken place here which gave them new faith in official tolerance for work that departs from traditions of socialist realism.

Last January, a group of young artists organized their own show at another district exhibition hall in Moscow, the first time artists, rather than officials, chose works for public showing.

"After the first few exhibits, we felt we could stop worrying," said Ivan Chuykov. "I was surprised they forbade anyone's works here today."

Every day now in Moscow, there are new examples of the fluctuating limits of glasnost. Just as the Belayeva exhibit was getting ready to open with the works of e'migre's, the editor of Moscow News, flagship of official glasnost in the Soviet press, was being chastised by Yegor Ligachev, the second-ranking man in the Kremlin, for printing a favorable obituary of Viktor Nekrasov, an e'migre' writer and former dissident who died in Paris. Ligachev is now established as the conservative voice on the Politburo in the debates over cultural liberalization and history.

Such battles are fought daily over the boundaries of the Soviet Union's new openness. A director of one avant-garde exhibition hall was issued a warning by the city's cultural department for a show she sponsored. This fall, she has decided to open a similar one. Elsewhere, a director ignored orders to remove works by a certain artist from the exhibit.

For members of the Moscow intelligentsia, the contradictions in Soviet culture today are no longer surprising: The point now is to test their limits.

"This exhibition is a result of the normalization process going on now," said one artist on Belayeva Street. "If the process had begun before, I think many of those who left would have stayed."