Heterosocial interactions, or social interactions with other-sex peers, are theorized to serve a number of unique developmental functions for adolescents (e.g., companionship, intimacy, experimentation with sex-role behaviors and sexual activity). Yet despite the importance of heterosocial competence in adolescent social development, there exists little research on the construct. Early research, although informative, reflects a narrow focus on heterosocial anxiety associated with date initiation situations. More recent research has broadened its purview to include investigations of the relation of heterosocial competence to the normative development of romantic relationships, as well as depression, anxiety, and violence in adolescent relationships. To facilitate further research, an expanded, well-defined description of the construct of adolescent heterosocial competence is needed that includes other-sex interactions in casual relationships, friendships, and romantic relationships. In this article we detail the historical and current definitions of the construct and encourage a broader understanding in the context of the developmental psychopathology framework. We follow with a review of our decade-long efforts to better operationally define and assess the construct by summarizing the development and validation of two measures: The Measure of Adolescent Heterosocial Competence and the Measure of Adolescent Heterosocial Competence-Young Adult Version. Finally, we suggest directions for future research. (Contains 2 tables.)