LEATRICE GILBERT FOUNTAIN, the daughter of the late silent screen star John Gilbert, will appear at The American Film Institute Theater this weekend to kick off its first-ever Greta Garbo retrospective, "Garbo at 80: The Complete Career." Author of "Dark Star: The Untold Story of the Meteoric Rise and Fall of the Legendary John Gilbert," Fountain will introduce and discuss the Garbo-Gilbert Flesh and the Devil (Friday at 6:45 and Sunday at 6 -- with live organ accompaniment both nights) and the double bills of Queen Christina and Romance (Friday at 9 and Sunday at 8:15) and Love and Anna Karenina (Saturday at 8:15 and Monday at 8:45). The series, timed to coincide with Garbo's 80th birthday on September 18, features all major works save 1928's The Divine Woman, which is a lost film.

The AFI will also pay tribute to "American Playhouse" with a series of Playhouse-produced films beginning Tuesday. On that date, American Playhouse executive director David Davis and executive producer Lindsay Law will speak at the 8:30 screening of the all-star production of Adventures of Huckleberry Finn. Both this film and Where Are You Going?, which will screen next Wednesday at 7, are being given their American premieres. Other prestigious films in the series include Gregory Nava's El Norte (September 7 at 6), Lynne Littman's Testament (September 8 at 6), and Michael Roemer's Haunted (September 9 at 8:45).

Tickets for all AFI Theater events are $3 for members, $3.50 for member's guests and $4 for non-members. For complete schedule information, call the box office at 785-4601.

Larry Lauria, who heads the Washington chapter of the International Animated Film Association, will begin an eight-week course entitled "Introduction to Animation" on September 5. To be held at Lauria's Animation House (716 Church Street in Alexandria), the class will meet from 7 to 9:30 p.m. and feature a hands-on 16mm film program covering character design and acting, movement, weight and timing. The $295 cost includes pens, pencils, film stock and all materials. To register, call Lauria at 684-1050.

The Production Center at Arthur Young will hold a seminar on "Contracts for Professionals" on Thursday from 7 to 10 p.m. at 1950 Roland Clarke Place in Reston. Sharon Winslow, assistant general counsel for the center, will speak on the ins and outs of contract format and negotiation, with particular applicability to media professionals. Cost is $25; space is limited. For registration and further information, contact Anne Polley at 703/620-4490.

According to the Washington-based Motion Picture Information Service, the area's 10 top- grossing pictures for the week ending August 22 were, i descending order, Back to the Future (continuing on 18 screens in its seventh week); Year of the Dragon (debuting at 20 houses); Pee-wee's Big Adventure (adding a screen to 17 in week two); The Return of the Living Dead (breaking wide at 22 houses); Volunteers (opening on 14 screens); Silverado (down from 16 to 14 houses in its sixth week); Real Genius (staying at 13 screens in week two); Summer Rental (up from 15 to 16 houses in its second week); National Lampoon's European Vacation (down from 18 to 15 screens in a full month of release); and Fright Night (down from 17 to 10 houses in week three).

In one of the more telling statistics of the week, Kiss of the Spider Woman earned a bit over $40,000 at two locations, while Columbia's The Bride made $44,178 -- at 19 screens.

Nationwide, latest estimates predict the summer's total business will hover around $1.39 billion, far short of the record $1.58 billion generated last year in the same period.

Your eyes and ears do not deceive you: That shot of Val Kilmer floating outside a window on some sort of balloon contraption that figured so prominently in the trailer for Real Genius was cut out of the finished film. And the music for the Summer Rental radio spot isn't from Alan Silvestri's score; it's a chunk of Dominic Frontiere's theme for Richard Rush's 1980 adventure comedy The Stunt Man.

In international production news (culled from various trade papers): Director Robert van Ackeren, whose A Woman in Flames played here late last year, has been fired from his newest picture, The Tigress, on the eve of the beginning of principal photography. The film, set to star Joanna Pacula ("Gorky Park") and Keith Carradine, will now be done by Swiss director Carl Schenkel. Production will begin in late October . . . Quincy Jones and Thomas Dolby will team up to create the score of Richard Brooks' new film, Fever Pitch . . . Jonathan Demme, who directed Stop Making Sense, seems to have discovered a whole new world of movie-making -- he's just completed three rock videos for John Cougar Mellencamp and the promo video for New Order's "The Perfect Kiss" . . . After 12 weeks on location in the Colombian jungle, Roland Joffe has completed principal photography on The Mission, with Robert De Niro and Jeremy Irons . . . Four-time Oscar winner Robert Wise has been elected president of The Academy of Motion Picture Arts and Sciences for the 1985-86 term.

North Carolina is the setting for some strange cinematic bedfellows this year: Danny Glover (Mose in "Places in the Heart"), Adolphe Caesar (Oscar-nominated for "A Soldier's Story") and Rae Dawn Chong (the sexy, crazy barfly in "Choose Me") have been added to the cast of The Color Purple, which began filming under director Steven Spielberg last month. Elsewhere in the state, Stephen King is gearing up to make his directorial debut with Maximum Overdrive, based on his short story "Trucks." Emilio Estevez will star, and the supporting cast will include some 150 18- wheeled vehicles. If the script follows the story, they'll all develop minds of their own and destroy a lonely truckstop . . . "Miami Vice" executive producer Michael Mann is preparing a detective story called Red Dragon (which he'll direct) . . . And Dino De Laurentiis has announced that he'll make King Kong II at his new production facility in North Carolina.

Ron Howard has begun filming Gung Ho for Paramount on location in Pittsburgh; Michael Keaton, the star of Howard's Night Shift, is top-lined . . . Leonard Michael's book "Men's Club" is being filmed by director Peter Medak ("The Ruling Class") with Roy Scheider, Frank Langella, Harvey Keitel, Treat Williams, Armand Assante, Craig Wasson, Richard Jordan and David Dukes in the cast.

PAGES OF FILM HISTORY -- Happy birthday this date to Shirley Booth, Fred MacMurray, Elizabeth Ashley, Peggy Lipton and Timothy Bottoms.

Those marking birthdays on Saturday include Daniel Schorr, Buddy Hackett, James Coburn, Warren Berlinger, Itzhak Perlman and Van Morrison.

Sunday's celebrants include animator Chuck Jones, Vittorio Gassman, George Maharis, Conway Twitty and Lily Tomlin.