A gifted, virtuoso comic, Robin Williams puts a barrier between his audience and himself, even as we laugh. In his good movies ("Popeye," "The World According to Garp," "Moscow on the Hudson"), strong directors keep him to a well-written character. At other times, he spouts jokes that distance him not only from the audience and his fellow actors, but even from his own character.

Director Levinson creates a fast-talking Armed Forces Radio d.j., Adrian Cronauer (Williams) in the Vietnam War. Hearing only his nonstop comedy, we know nothing about him. Where is he from? What did he do before the war? His entire world has become material for his show. Levinson lets Williams improvise from the script, then edits for the best takes; his scenes are riotously funny. But Levinson also subtly peoples the scenes with complex, human characters, setting a trap: Adrian is forced to reveal human emotions.

He resists. When his Jeep breaks down in the middle of the Viet Cong jungle, he spouts one-liners to trees. Meeting a young Vietnamese woman, he uses one-liners on her, too, although she doesn't get them. He wisecracks in run-ins with Army brass, who don't like his anti-establishment streak on the air; he insists he's "always on." Nothing, not even war, has intrinsic value for him; it's all just "material."

But things start happening. To impress the young woman, he starts an English class; it turns out he likes the Vietnamese. He barely survives a horrific terror attack, then is removed from the radio. Meeting young, admiring soldiers as they go into battle, their eyes makes him take himself seriously. By the end of the movie, Cronauer is a better, deeper man.

Its semi-sad love story notwithstanding, the film is great comedy, similar to "M.A.S.H." But the main thing is that Cronauer changes: His humor becomes a tool for doing good, not just his way to hold an audience. Confronting the need that compels the least-secure people on Earth to try to make us laugh - controlling us, because they need to prove their power - the movie shows Cronauer acting funny deeds as therapy for his low self-esteem. By its end, he doesn't wisecrack all the time, any more; he no longer needs to, and no longer thinks he's a worthless (albeit bright, funny) sad sack. Early on, the character's eyes seem dull; by the end, they have vision.