The two 17-year-old best friends at the center of Alfonso Cuaron's wonderful "Y Tu Mama Tambien" are obsessed with sex and bursting with callow braggadocio, their machismo a cover-up for inexperience. It's summer, their girlfriends are traveling in Europe, and Tenoch (Diego Luna), the upper-middle-class son of a corrupt politician, and Julio (Gael Garcia Bernal), who comes from a more modest background, are looking for adventure. They find it in the seductive form of 28-year-old Luisa (Maribel Verdu), the wife of Tenoch's distant cousin. To the boys' amazement, she takes them up on their invitation to accompany them to a faraway beach--Boca del Cielo--whose existence they've invented.

Tenoch and Julio's wildest fantasies come true when Luisa (for reasons we only gradually discover) sleeps first with one, then the other--but their answered prayers lead them to realizations about themselves neither wants to acknowledge. The eroticism in Cuaron's road movie (which broke all box-office records in Mexico) is the real deal: tactile, sexy, psychologically charged. It's not there to shock or provoke giggles--this is no Hollywood teen comedy--but to illuminate these complex, poignant and lost characters.

Cuaron (who made "A Little Princess" in Hollywood) wrote the screenplay with his brother Carlos. Using a narrator, they set this bittersweet odyssey in a broader context: out of the corners of our eyes, we glimpse a portrait of contemporary Mexico--a place of roadblocks, arrests, student demonstrations, casual corruption--that his teenage heroes are oblivious to. "Y Tu Mama Tambien" ("So's Your Mother") is light on its feet (the political subtext is almost subliminal), shot in a lyrical, freewheeling style by cinematographer Emmanuel Lubezki. But the easygoing surface is deceptive. The movie has an emotional kick that lingers like a primal memory. When the year is over, Cuaron's film will be remembered as one of 2002's finest.