Although researchers have investigated how adolescents' friendships affect their romantic relationships, the influence of romantic relationships on friendships is unexamined. As a first step, 9th- (n = 198) and 11th grade students (n = 152) reported on their conceptions of friendship when one friend had a romantic relationship and when neither friend had a romantic relationship. As predicted, adolescents believed friendships in which a friend was dating would be characterized by less positive features and more negative features than friendships in which neither friend was dating. Additionally, older adolescents thought romantic relationships were more damaging to companionship and corumination than did younger adolescents. The closer nature of older adolescents' romantic relationships may result in lower quality friendships or older adolescents may be more aware of the potential negative consequences of romantic relationships for friendships. Girls viewed friendships as higher in conflict-rivalry and lower in corumination when one friend was dating while boys did not. And although girls and boys viewed friendships as lower in intimacy and companionship when a friend has a romantic partner, the difference was greater for girls than boys. Girls may be more sensitive to the effects of a friend's romantic relationship on their friendship than are boys. Findings necessitate theories of close relationships that incorporate age and gender as important variables.