Eleventh- and twelfth-grade adolescents (N=18) were videotaped during same-sex and opposite-sex interactions. In both grades, females felt more comfortable during same-sex interactions and rated their same-sex partners more positively than did males. Females in both grades and eleventh-grade males showed more peer intimacy than did twelfth-grade males. Eleventh-grade females showed more playful behavior. More synchrony was found for animated state in twelfth graders. (Author/MKA)