"ER" star Julianna Margulies has joined the cast of Jon Robin Baitz's new play Ten Unknowns. As first reported on Playbill On-Line on March 1, the Baitz drama will star Jason Robards and be presented at Lincoln Center Theater.

Ten Unknowns will open on Feb. 26, 2001 and run through April 15, reported Variety.

In the play, Robards will play a once promising, now obscure painter, living in Mexico. Margulies is a researcher studying a breed of frog that is on the verge of extinction. The two meet and become lovers.

Baitz's A Fair Country was seen at LCT a few seasons back. Since then, Manhattan Theatre Club has staged his Mizlansky/Zilinsky, while his adaptation of Ibsen's Hedda Gabler was seen in L.A., in a staging starring Annette Bening. Baitz's other works include The Film Society and The Substance of Fire.

Robards last New York appearance was in Brian Friel's Molly Sweeney at the Roundabout Theatre Company's Laura Pels Theatre. Other recent stage turns have included Pinter's Old Times and Horowitz's Park the Car in Harvard Yard. Robards if famous for creating or recreating many characters in the O'Neill canon, including Long Day's Journey Into Night and The Iceman Cometh. He also appeared in the original production of Arthur Miller's After the Fall and won a Tony for his performance in The Disenchanted. Margulies will leave the long-running "ER" in May.

--By Robert Simonson