ANOTHER anniversary has rolled around. The AFI Theater will celebrate 10 years of sometimes troubled but ultimately thriving and stable existance with a six-week commemorative series called "Our First Decade," which begins Thursday.

Michael Webb, the original programming manger for the theater, estimates that more than 5,000 titles have been projected for the entertainment or edification of members and guests during the decade. The 70 or 80 titles in the anniversary series represent a cross-section of the theater's programming tendencies. There are examples of classic revivals, surveys of foreign-film industries, career retrospectives of individual performers and filmakers, local previews of the neglected or underrated or avant-garde, surveys of historical periods and social topics or specific film genres, traditions, crafts and techniques.

Some only-at-the-AFI-Theater events are naturally more appealing than others. The prospect of seeing "Gone With the Wind" in a mint-condition 35mm print enchanced by Olivia de Havilland's personal appearance, is somehow more inspiring than the prospect of a week's immersion in the new Bulgarian cinema. Nevertheless, these extreme cases illustrate the theater's undeniable importance to the movie culture of the city. Certain special events and certain kinds of specialized programming are only possible on a systematic basis at the AFI Theater, and the cumulative effect is to enrich and diversity local filmgoing opportunities.

Webb believes that the successful example of both the AFI Theater and its touring programs may soon lead to the creation of a permanent affiliate institution in Los Angeles. Adam Reilly, who has surpervised programming at the AFI Theater for the past 2-1/2 years, moves to Denver next week to establish a repertory cinema at the city's new arts center. While wishing Reilly great success, it's also a great pleasure to learn that former programmer Michael Clark will be returning on Feb. 1 to replace Reilly and once again enliven the AFI Theater with his programming brainstorms and tangy program notes.

"Our First Decase" opens and closes with the two silent classics that opened and closed the phenomenally popular inaugural series of the AFI Theater at the National Gallery of Art in January 1970: Erich von Stroheim's stylish, inimitably perverse production of "The Merry Widow" and D.W. Griffith's pioneering, overreaching epic "Intolerance." That first series consisted of 12 films recently restored as part of the AFI's archival and preservation programs.

AFIdirector George Stevens Jr. (the son of the noted filmmaker who directed "A Place in the Sun," Shane" and "Giant") announced the establishment of the theater on Dec. 1, 1969. The opening season was to consist of six programs lasting eight days each, scheduled for one week every month from January through June in the auditorium of the National Gallery. The response was so overwhelming -- over 3,000 membership applications within a month and an immediate sell-out of the first series -- that the AFI was compelled to suspend membership solicitation temporarily and to add a second week. The programs announced for subsequent months were either stretched to two weeks or supplemented by a second series.

A success at the National Gallery, the AFI Theater expanded to full-time, daily operation in September 1970. Unfortunately, the prospects went from bullish to bearish almost immediately, because Webb found himself with more theater than he needed in a hard-luck location. Roger Stevens, then an AFI trustee, had negotiated a two-year lease for an attractive, beautifully equipped theater constructed at L'Enfant Plaza as a Washington flagship by General Cinema Corporation, the largest theater chain in the country.

There were a few catches: L'Enfant Theater had about 800 seats, compared to 300 at the National Gallery; the site already had failed as a showcase for first-run features; there was little night life at L'Enfant Plaza and an intensified fear of crime in the city itself; the movie business in general was heading for a depression in the fall of 1970. L'Enfant was destined to remain an enticing but unsuccessful location. The upshot was a weekly box-office deficit that threatened the AFI Theater with an annual deficit of $100,000 and imminent extinction.

The caliber of programming didn't decline at L'Enfant. Memberships climbed to about 6,000. The average attendance remained what it had been at the National Gallery -- a shade over 200 customers a performance -- but in a large commercial house this figure did not generate nearly enough revenue to meet expenses. By economizing and appealing for donations, the AFI hung on at L'Enfant until assured of the permanent location Stevens always had desired -- a place at the Kennedy Center.

A grant of $250,000 from the late Jack Warner financed the construction of a modest but distinctive, comfortable and practical theater, seating 224, in a backstage cavern of the Eisenhower Theater. THE AFI Theater closed shop at L'Enfant in June 1972, then resumed full-time programming at the new Kennedy Center auditorium on April 3, 1973.

Webb's ambitious opening series included American premieres of several new features. Unfortunately, the first of the new features on the program -- Costa-Gavras' "State of Siege," scheduled for a single performance on the third night of the series -- proved unacceptable to his boss.

Stevens had become alarmed when he read a European review of the film, a fictionalized chronicle of the kidnapping and execution of Agency for International Development official Daniel Mitrione by Tuparmaro guerillas. After screening it, Stevens decided to cancel "Siege" on the grounds that the filmmakers tended to "rationalize an act of political assassination," rendering the movie "undersirable and inappropriate" to be the first new film shown in a building dedicated to the memory of President Kennedy.

Predictably, this cancellation provoked several others, as about half a dozen filmmakers withdrew new work from the series in the traditional Gesture of Solidarity. It was never clear whether Stevens would have permitted "State of Siege" to be the second or third or 15th new film shown at the theater. Probably, not. "State of Siege" never has played at the AFI Theater. It was scheduled to open at the Outer Circle the day after its premiere at the Kennedy Center anyway. Costa-Gavras and screenwriter Franco Solinas arrived in town to promote their movie and dispute Stevens' interpretation, which seemed debatable.

Importer and co-producer Donald Rugoff also arrived to help promote the opening and accuse Stevens rather overdramatically of censorship, a charge the director made a point of denying in advance. What with the cancellations, recriminations and publicity, the gala opening series was transformed from a welcome event into a melancholy fiasco.

Despite this unhappy, debut, the AFI Theater found its niche at Kennedy Center. It has stood the test of time better than "State of Siege," but then it always figured to. The movie itself never lived up to the controversial reputation it took away from Stevens' blackball.

For the record, the theater still runs at a deficit of about $100,000 a year, the amount regarded as unthinkable at L'Enfant. Ironically, this deficit seems tolerable within the permanent, respectable structure of a Big National Cultural Institution like Kennedy Center. The local AFI membership has increased steadily to about 19,000 (out of a national membership of about 100,000). The annual shortfall is subsidized by angels and the fund-raising showings sponsored by Ina Ginsburg's Fans of the AFI.

The theater doesn't need to become self-supporting to rationalize its existence, and many of its programs would be impossible without the cooperation of filmmakers, distributors, foreign governments and local exhibitors. Its purpose should be to remain uniquely stimulating. That purpose has been realized in the first decade of operation, and one trusts that it won't be betrayed in the decade to come.