Whoopi Goldberg is at her most appealing in "Boys On the Side," but the film is, sadly, a terribly uneven affair, a soap opera-comedy that is at its best in the first third or so, as a "Thelma & Louise"-style road comedy. But when it becomes a lecture on AIDS and tolerance — and worse, a courtroom drama — the film sinks into bathos.

"Boys On the Side" begins as Goldberg, a lesbian lounge singer, is about to embark on a driving trip from New York to Los Angeles. She's looking for someone to share expenses and time behind the wheel when she links up with a most illogical candidate in the form of straight, mild-mannered, frail-looking Mary-Louise Parker. ("The whitest woman in America," Goldberg calls her.)

Before they get very far, however, a detour brings them to the home of a young friend of Goldberg's (Drew Barrymore), an abused woman who, with help from Goldberg and Parker, leaves her drug-dealer boyfriend tied to a chair and joins the ladies on the road.

Later, however, when the guy is found dead, they find themselves on the run, thinking they have killed him.

There are some very funny comic adventures in the early stages of "Boys on the Side," and some feel-good moments as the members of this unlikely trio learn to trust each other. But then, the film takes a dramatic shift in tone as they find themselves stuck in Tucson, Ariz., when one of them is hospitalized with AIDS.

As they reluctantly settle in Tucson, all three make new friends, find their relationships with each other on the rocks and, ultimately, through incredibly contrived and idiotic circumstances, wind up back east again when Barrymore goes on trial for murder, leading to an overly sentimental finish.

There are some poignant moments that work, and an awful lot of attempts that fail. There are also stereotypes galore, overcome to some degree by the performances of the first-rate cast.

Goldberg, Parker and Barrymore are a wonderful team, and there are some big laughs in the film's first third. Too bad it goes all preachy and mushy on us, with moments that may make the audience wince.

"Boys on the Side" is rated R for violence, sex, nudity, profanity, vulgarity and marijuana smoking.