This study used a social exchange framework to examine the features of non-romantic other-sex (OS) friendships compared with same-sex (SS) friendships and romantic relationships. High school seniors (N = 141) completed open-ended interviews about the benefits and costs of having OS friendships, SS friendships, and romantic relationships in general. As expected, perspective taking, learning about the other sex, and meeting the other sex were seen as rewards of OS friendships more often than for SS friendships and romantic relationships. Confusion about the nature of the relationship was seen as a cost of OS friendships more often than of SS friendships and romantic relationships. Intimacy, support, and companionship were mentioned less often as rewards of OS friendships than romantic relationships. Adolescents also completed questionnaires about their own specific relationships of each type. Their OS friendships were perceived as less supportive than their other two relationships; OS friendships were also seen as having fewer negative interactions than romantic relationships. Our findings expand the application of social exchange theory and lend empirical support to prior speculations about OS friendships and their importance in adolescents' social worlds.