"It was here in the United States that I started to become politically conscious," Santiago Alvarez once said, "and when I went back to Cuba I became a Communist. American imperialism is the greatest promoter of communism in the world."

Alvarez, 58, a famous documentary filmmaker and vice president of the Cuban Film Institute, was in town yesterday with a number of colleagues and some cans of film.

Few Americans have seen any Cuban movies at all, because of the cultural blockade against the Castro regime. But in 1973 one charming film got through: Thomas Alea's "Memories of Underdevelopment," about a rich young man who elected to stay on in Havana and confront the revolution, and later we saw Humberto Solas's "Lucia," which showed how Cuba has dealt with women over three centuries.

Gradually, more pictures appeared through the efforts of the Tricontinental Film Center and the Center for Cuban Studies, and they gave a tantalizing glimpse of a film culture curiously reminiscent of the Russian Revolution's Brilliant explosion of talent: Eisenstein, Pudovkin, Dziga Vertov and so on.

For the next week, Washington can see eight new Cuban feature films plus "Underdevelopment" and "Lucia" at the Key Theater, 1222 Wisconsin Ave. N.W.

The eight pictures, which have won awards all over the world, are having their American premieres in five cities this spring. Very generally, they illustrate two major strains in Cuban film: the emblematic panorama of some historical event and the hard realism of contemporary Cuba, often in black and white.

For example, "Cantata de Chile" depicts the 1907 strike by nitrate workers that ended in the Iquique Massacre and relates it to the struggle of workers in that country from the days of the Conquistadors to our own time.

The Solas film is done as a pageant, with dramatic shots of marchers holding flags, in the manner of Soviet and Maoist posters, and an operatic pace relieved now and then by vivid glimpses of individual people caught up in the fight: the worker leader arguing with the English mine owners, the woman frantically collecting hoes, sickles and clubs to fight machine guns.

In contrast, "One Way or Another," directed by the late Sara Gomez Yara, shows in the most direct terms the impact of the revolution on the marginally indigent of Havana. It could be a tract, but it is not. We are brought into the lives of real people (many of them nonactors) and their daily concerns: their jobs, their love affairs, their friends.

"Social consciousness" is an easy cliche, heard frequently in countries like Cuba. This picture makes the cant phrase into something real, the conflict between loyalty to a pal and loyalty to one's fellow workers.

Sara Gomez died at 31 just before completing this film, and Alea dedicated his new picture, "The Last Supper," to her. Alea's work is perhaps better known to Americans than any other Cuban filmmaker, for besides "Underdevelopment" he did "Death of a Bureaucrat" and "A Cuban Fight Against the Demons," both distributed here.

"One Way or Another" bears the hallmarks of Cuban film: the documentary approach - documentaries being the pride of the business - and the humor. We are introduced to Guillermo Diaz, once a top fighter (Golden Gloves, 1957), now a folksinger and street person, one of those people swept into the revolution as was Alvarez himself. And we get a taste of the wry, pleasant Cuban humor, the observation of human foibles without bitterness.

The same strains are apparent in "The Teacher," by Octavio Cortazar, about a 15-year-old student assigned to teach illiterate villagers during the Cuban Year of Education, 1961. Though the picture wanders off into a Cuban view of the Bay of Pigs and related violence, it remains a warm and accurate view of a young man growing up.

One could say, in fact, that humor is what separates Cuban film from most other revolutionary film. Anyone who has seen the short, "For the First Time," about the visit of a mobile filem projection unit to a remote village and the peasants' first goggle-eyed exposure to a Chaplin movie, can't help but wonder why we must be so hostile to whatever we don't understand.

Seven of the new films, plus "Underdevelopment" and "Lucia," will be shown at the Key through Tuesday. And May 10 through 16 the great Alea historical drama, "The Last Supper," based on an 18th-century uprising at a Haven sugar mill, will be screened nightly.