Antipathetic relationships and friendships are common during adolescence. One type of antipathetic relationship that has received no empirical attention is one that emerges from a broken friendship. Two studies, a reanalysis of N. A. Card's previously published data (Study 1) and newly collected data (Study 2), investigated this topic through mixed-methods analysis of emerging adults' retrospective reports of relationships during high school. Qualitative analyses revealed jealousy, incompatibility, intimacy-rule violations, and aggression as themes in the transformation of friendship to antipathy. Quantitative analyses revealed intimacy-rule violations in the formation; relational aggression, competition, and avoidance during the maintenance; and continued contact following high school as more common for former friends. These findings highlight the dynamic relations between friendship and antipathy. (Contains 3 tables.)