Two studies were conducted to examine the relations between similar minority groups. We predicted that minority group members would show horizontal hostility, a form of prejudice, against members of a similar, but more mainstream, minority group. The results of both studies confirmed this hypothesis. In Study 1, members of 3 Jewish congregations (reform, conservative, orthodox) showed prejudice against a member of a similar but slightly more secular congregation. In Study 2, members of a college varsity soccer team showed prejudice against junior varsity players. We conclude by suggesting that horizontal hostility is the result of social changes since Allport (1954) wrote The Nature of Prejudice. Members of minority groups value their minority social identity, even when the group is stigmatized. The positive value of minority social identity causes group members to look down on members of similar, more mainstream groups.