Over the past two decades, New York's Ensemble Studio Theatre has fostered the creation of more than 5000 new plays. Thirteen more are on view at E.S.T.'s annual festival of one-acts, "Marathon `98," which runs, in three series, May 6-June 14. Casting and directors for the third and final series of plays have just been announced and include a David Mamet premiere and Leslie Ayvazian starring in her own solo.

Here's the line-up for Series C of the E.S.T. One-Act Marathon, June 3-14:
The Jade Mountain by David Mamet
E.S.T. artistic director Curt Dempster directs this drama about a Vietnam veteran struggling to remember both childhood traumas and wartime horrors. James Murtaugh and Chris Ceraso star. Mamet's best-known works include Speed The Plow and Oleanna. His Old Neighborhood closed recently on Broadway.

Plan Day by Leslie Ayvazian
Ayvazian plays a single mom who (in the play's 20 minutes) goes from the 20's to the 70's. Other Ayvazian works include Nine Armenians and Footlights.

The Earthquake by Elinor Renfield & Joyce Carol Oates
Renfield directs this piece based on Oates' story of a divorced couple and their son's sense of abandonment. James DeMarse, Patric eri and Joseph Siravo star.

Mary MacGregor by Keith Alan Benjamin
Annie O'Sullivan and Andy Weems star in this drama about a woman haunted by the spirit of her husband. Joe White directs. Prelude To A Crisis by Ari Roth
Shades of Oleanna and Wang Dang pervade this tale of a teacher and a student meeting in a motel room. Greg Germann and Melinda Page Hamilton star in this play by Ari Roth, author of Born Guilty and Goodnight Irene. Mark Nelson, of Proposals and Picasso at the Lapin Agile fame, directs.

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Among the other noted writers contributing new works to this 21st annual event were Paul Rudnick, Shel Silverstein, Billy Aronson, Keith Alan Benjamin, Elizabeth Diggs, Prince Gomolvilas, Jennifer Mattern, Barbara Sundstrom and David Zellnik.

Horton Foote, author of A Trip To Bountiful and the Pulitzer winning The Young Man From Atlanta, has called E.S.T., "a constant creative force in the American theatre where one is sympathetically encouraged to develop his talent and craft. Among those developing both at E.S.T., were Howard Korder, Steve Martin, Robert Schenkkan (The Kentucky Cycle) and OyamO.

For tickets ($15 per series) and information on Marathon `98 at Ensemble Studio Theatre call (212) 247 4982.

-- By David Lefkowitz