Harry Stack Sullivan maintained that competition between friends in early adolescence would generally destroy their friendship. Working with early adolescent samples in Canada, Costa Rica, and Cuba, we found that hypercompetitiveness—a form of competition involving the need to prove one's own superiority—was linked with conflict between friends, with termination of friendship, and, in general, with less closeness. However, simple enjoyment of competition with a friend was unrelated to friendship continuation. There were important gender and cultural differences in both the levels of competitive behavior and in the mediators between competition and friendship continuation. In general, girls were less competitive with their friends than were boys. Path analysis revealed that both closeness and conflict mediated the link between hypercompetitiveness and the continuation of friendship. Several dimensions of competition were associated with greater companionship in the friendships of boys, especially in the Canadian sample, but were negative correlates of companionship between female friends.