A meta-analysis examined the extent to which socio-structural and psycho-cultural characteristics of societies correspond with how much gender and ethnic/racial groups differ on their support of group-based hierarchy. Robustly, women opposed group-based hierarchy more than men did, and members of lower power ethnic/racial groups opposed group-based hierarchy more than members of higher power ethnic/racial groups did. As predicted by social dominance theory, gender differences were larger, more stable, and less variable from sample to sample than differences between ethnic/racial groups. Subordinate gender and ethnic/racial group members disagreed more with dominants in their views of group-based hierarchy in societies that can be considered more liberal and modern (e.g., emphasizing individualism and change from traditions), as well as in societies that enjoyed greater gender equality. The relations between gender and ethnic/racial groups are discussed, and implications are developed for social dominance theory, social role theory, biosocial theory, social identity theory, system justification theory, realistic group conflict theory, and relative deprivation theory. (Contains 6 tables, 5 figures, and 1 footnote.)