Fourteen plays will be released as films over the next two years in what will be "one of the strongest cycles of stage-to-screen transitions in recent times," reports Variety. Many of the plays have had recent productions on Washington stages, including "Extremities," "Brighton Beach Memoirs" and " 'night, Mother."

Motion picture producers, notes the report, attribute the increase in theatrical film adaptations to the view held by many big-name actors that certain dramatic properties are important "career vehicles," and to their willingness to make significant up front salary concessions to ensure the projects' successes.

Among such box-office draws slated to appear in films based on plays are recent Oscar-winner William Hurt ("Children of a Lesser God"), Al Pacino ("American Buffalo"), Rob Lowe ("Sexual Perversity in Chicago") and Sissy Spacek, Diane Keaton and Jessica Lange ("Crimes of the Heart").

Box Office Business

Three area productions are doing a boom business for their theaters. Arena's "The Wild Duck," which has been extended through April 27, is "one of the most popular shows ever done in the Kreeger . . . selling out well in advance," according to spokesman Shawn Fraser, who noted there are still tickets available for performances later in the run. Through three weeks at the Studio, "The Birthday Party," which has been extended through April 20, was keeping pace with last fall's "Playing for Time," "one of Studio's best sellers in the last few years," said spokeswoman Marilyn Newton. And at the Source Theatre, not known for the longevity of its productions, an aberration: "Beyond Therapy" has been extended through May 10. According to spokesman Phil Setren, the play recently set a single-night box office record for the Warehouse Rep at $1,288, demolishing the previous record of $1,149.25 set by "Equus" in 1983.

'Behind the Scenes' Trade Fair

The Actors Center will hold its third annual trade fair -- "Behind the Scenes" -- Saturday and Sunday at the Washington Convention Center. The event will feature workshops, panel discussions, exhibits, a theatrical flea market and live performances. For information or reservations, call 638-3777.

International Festival

Baltimore will host the 20th biennial Theatre of Nations, an international theater festival coming to North America for the first time, June 15-28. Among the dozen theater companies scheduled to perform on Baltimore's stages are the National Theatre of Great Britain, which will present the U.S. premiere of "Animal Farm," a musical version of George Orwell's novel; and Japan's Suzuki Company of Toga, which will present the Greek tragedy "Clytemnestra." For further information call (301) 625-4270.

Hexagon's Record 'Roast'

The 1986 Hexagon revue, "Roast of the Town," raised $140,000 for the Hospital for Sick Children -- the largest charitable contribution in Hexagon's 31-year history. This year's move to the larger theater at the Duke Ellington School of the Arts helped Hexagon set a new record of more than 15,000 tickets sold. Theatergoers can get ticket information for the 1987 Hexagon revue, which will benefit another Washington charity, by calling 642-9317.

Odds and Ends

Katherine Faith Prior has been named director of the Father Hartke Legacy, which was founded to carry on the late Rev. Gilbert V. Hartke's commitment to scholarships for drama students and young men entering the priesthood; for information call 829-7527 . . . The Arena Stage Guild's spring benefit last Saturday at the Westin Hotel raised more than $55,000 for the theater . . . Helen Hayes will make a guest appearance at a benefit for the Wye Mills Theater (which hopes to reopen this summer) April 26 at Chesapeake College; for ticket information call (301) 827-8822 after 5:30 p.m. . . . Arena Stage will present a free symposium -- "Ibsen, Our Contemporary" -- Monday at 8 p.m. in the Kreeger; call 488-3300 . . . "The Miser" begins previews tonight at the Shakespeare Theatre at the Folger . . . "The Zulu and the Zayda" starts previews tomorrow at the Jewish Community Center of Greater Washington . . . "Johnny Bull" opens Friday at Horizons Theatre.