Ben Butley, the sarcastic, soured English professor who hides his own hurt and loneliness under a veneer of mocking wit, is a meaty and demanding role for an actor.

And what a vravura performance Martin Goldsmith is giving in the Source Theatre production of Simon Gray's biting comedy, "Butley." He dominates the stage, tossing stinging barbs at others, unmindful of the cruelty. It is his way of "having fun," Butley explains in denying that he is a troublemaker.

Goldsmith's performance as Butley (a role portrayed on the screen by Alan Bates) is first-rate. He lounges in his chair disdainfully and dismisses an overearnest student's thesis with a raised eyebrow. He is a bitter, self-destructive man who shows off his superior education with sneering remarks. But underneath this front, Goldsmith catches the fear and emptiness of Butley's life.

We meet Butley on one day in his life as a professor at an English university. It is the day that he is to learn that his wife of a brief marriage wants a divorce to marry a schoolmaster dismissed by Butley as "the dullest man in London." More crushing, he is to learn that his protege is leaving him for another gay lover.

Butley is about his usual malicious mischief. He capriciously lures a student to his tutorial direction, stealing him from a woman professor who isn't very exciting in the lecture hall. He tries to discredit his protege's new lover. He makes nuisance calls to the school of his wife's new suitor. He reduces a girl student to tears with his comments on her thesis. All the while he is having his "fun" with pointed quotations and remarks.

Goldsmith's impressive presence -- he is on stage throughout -- is backed by several strong performances, including Steven Dawn's sensitive portrayal of Joey, the protege and homosexual partner of Butley. It is not a flamboyant part but it is pivotal to the play's success. Also supportive in their roles are Patti Chambers as the overzealous student, Kathleen Weber as the wife, and Nicholas Mathwick as Reg, who becomes Joey's new lover.

John Jacobsen has paced the pay beautifully. The only discordant notes in this splendid production come in the stage interpretation of two roles: Edna, the woman professor, and Mr. Gardner, the new student lured to Butley for tutorials. Edna (played by Beverly Brigham Bowman) is introduced as a flutter-headed, menopausal woman professor. This denies her the pathos in the later scenes, as captured by Jessica Tandy on the screen. And Jamie Lawrence's Mr. Gardner has overplayed mannerisms that cast doubt that Butley would have talked to him for very long even in a pub.

Mr. Gardner has to offer some hope if we are to feel the impact of Butley's last lines as he dismisses the new student: "I don't want to start again . . . I'm too old to be playing with the likes of you."

"Butley" is rotating in repertory with two other plats at the Source Theatre, 1809 14th St. NW. The rep series will run through May 10 on a revolving schedule that makes it best to check by phone (462-1073) on performances dates.