THE KEY THEATER will move Shoah, described by some as "a monument to the living and the dead of the Holocaust," into one auditorium rather than two beginning January 10 to make room for the German-made Year of the Quiet Sun.

"Shoah," a 91/2-hour Claude Lanzmann documentary shown in two parts, has been profitable for the popular Georgetown theater.

"It's been outstanding. We've had excellent crowds," says Joanne Bauer, office manager for the Key. "We decided to continue the matinees because business has been so good."

Part One screens Wednesday through Saturday and Part Two Sunday through Tuesday. Admission to each part is $10. (Call 333- 5100 for showtimes.)

"Shoah" is expected to run at least through January 16. The theater's owners want to keep the film longer but are being pressred to return the prints because the film's distributor has scheduled openings in other cities.

The Key will also open the successful Japanese epic Ran on January 24. The film reportedly has played to packed New York houses since it opened last week.

The American Film Institute, dark for the past week, reopens Friday at 6:30 with Humphrey Bogart as Sam Spade in the 1941 blockbuster The Maltese Falcon. Based on the story by St. Mary's County, Maryland, author Dashiell Hammett, the film was directed by John Huston and also stars Peter Lorre, Sydney Greenstreet and Mary Astor. The 100- minute film also screens Tuesday at 8:30.

It's the opening shot in the "Hollywood Gumshoes" series that continues Saturday with Bogie's The Big Sleep at 6 and again on Wednesday at 8:30. Call 785-4600 for a recorded schedule.

Beginning in January, Roth Theaters will offer free tours of selected theaters.

"We're hoping to stimulate interest in the movie business," says spokeswoman Amy Cubert. She says the tours will be geared toward schoolchildren, senior citizen groups and other education-oriented groups of 25 or more. The tours will cover complete operation of a movie theater, from obtaining the film to running the concession stand and operating the projectors. The tours end with a short feature film. Call 587-8450 to book one.

Several weeks ago this column mentioned that despite strong VCR sales, new movie theaters continued to be built in the Washington and Baltimore area. Now California-based MCA Inc. and Cineplex of Toronto have announced that they will spend $10 million to build the world's largest cinema complex in the Universal City section of Los Angeles. The plan calls for a two-story, skylit theater with 17 wide screens, 5,600 seats, vast lobbies, two cafes and parking for 1,400 cars. The complex is scheduled to open in June 1987.

Business is booming for Cineplex. In November, the company purchased he Plitt Theatre Circuit, the nation's fourth-largest movie chain with 608 screens at 210 houses in 21 states. The deal made Cineplex, which also runs 492 screens in Canada, North America's largest theater operator.

Meanwhile, MCA presented its common- stock holders of record on December 24 with a Christmas bonus, a quarterly cash dividend of $.17 per share payable January 13. Last August shareholders enjoyed a 3-for-2 split.

Down and Out in Beverly Hills, starring Nick Nolte, Bette Midler and Richard Dryfuss, with Little Richard making his film debut, will get in a sneak preview on New Year's Eve at the NTI Tysons Corner at 8 p.m. The event is being sponsored by radio station WAVA (105.1 FM), which is giving away 100 pairs of tickets. The movie's scheduled to open in Washington on January 31.

SHORT SUBJECTS -- The Baltimore Museum of Art on Art Museum Drive in Baltimore will screen The Lost Honor of Kathrina Blum Friday evening at 8. Cost is $3.50 for the general public; $2.50 for museum and Film Forum members. Call 301/396-6314 . . . The "Down Under" film festival continues at the Biograph in Georgetown with Utu showing through January 6. Call 333-2696 . . . The National Air and Space Museum's "Comet Tales" film series skips this Friday but returns to the Langley Theater screen next Friday at 7:30 with Rocketship X-M made in 1950 and starring Lloyd Bridges . . . The Jewish Community Center of Greater Washington on Sunday will screen Almonds and Raisins, a new film chronicling the Yiddish cinema. Showtime is 7:30 p.m. at 6125 Montrose Road, Rockville. Seats are $2.50 for members, $3.50 nonmembers. Call 881-0100.