TEEN MOVIES come of age in "Smooth Talk," not just another youth movie, but a deft dramatization of a Joyce Carol Oates story adapted by a couple of documentary filmmakers in their feature debut.

It concerns the long hot summer of 15- year-old Connie, played by Laura Dern, who's as sure in the role as a teen Meryl Streep. It's a performance of quiet depth and intensity that augurs a brilliant career for the young Dern (the blind girl in "Mask" and daughter of Bruce).

Treat Williams costars as the older man, on the 30ish side, who seduces Connie that summer, soiling the magic and the mystery, and introducing her to the struggle for sexual power.

The story is gentle and comic at first, concentrating on a conflict between Connie and her mother Katharine, played by Mary Kay Place. The two clearly love each other, but Connie, like most teenagers, is struggling for her independence from the family. As the relationship between mother and daughter breaks down, to Katharine's dismay, boy- crazy Connie turns to men.

It's only natural. But Katharine is losing her daughter, and at the same time, there's a sadder element in the conflict between the two. Connie is brand new, just forming; Katharine is beginning to fade. And she doesn't really know why she's so mad at her little girl.

In one of the film's best scenes, Connie dances to "Handyman," grinding ecstatically, and the camera cuts to Katharine, overhearing in the kitchen, swaying in a half- remembered echo. "I look in your eyes and all I see are trashy dreams," says the mother who dreamed them too.

The mood grows progressively darker as Treat Williams, playing a trashy dreamboat, drives up in his LeMans convertible. Oily, persuasive and a little scary, he talks Connie into taking a ride, finally seducing her through the screen door.

The acting is sure, and we feel the torment in Connie's mind, as she leaves with this James Dean throwback who calls her my "sweet blue-eyed girl." "What if my eyes were brown?" she whispers in a wise, already womanly retort.

Matching Dern in her stunning performance, Williams is in his best role since "Prince of the City." Place, broken-hearted when her daughter rejects her, seems a touch too uptown for this role of has-been home-renovating mother destined to a life of drabness.

Levon Helm, a disconcerting, southern- country character, is slightly out of context as the dad. And Elizabeth Berridge of "Amadeus" is miscast as Connie's older sister, who looks far younger than Dern. It ruins their scenes together, but she does convince us that she's the favored family pet.

Joyce Chopra directs the adaptation written by her husband and partner Tom Cole of "Medal of Honor Rag," using documentary methods that make this film as cozy as a sad little French comedy.

Though its moderate budget shows some in the quality of the color, the photography by James Glennon is artful and frankly sexual, sometimes stalking its heroine like a horror movie slasher down a dark hall. It stalks her as surely as her adulthood stalks her adolescence and innocence gives way to age.

The just-released "Pretty in Pink" shows us a prim Cinderella at prom time, but "Smooth Talk" shows us a real teenager whose sexuality seems to take her over, and whose climactic awakening might be some wicked daydream.

SMOOTH TALK (PG-13) -- At the Key.