In 1993 Oliver and Hyde conducted a meta-analysis on gender differences in sexuality. The current study updated that analysis with current research and methods. Evolutionary psychology, cognitive social learning theory, social structural theory, and the gender similarities hypothesis provided predictions about gender differences in sexuality. We analyzed gender differences in 30 reported sexual behaviors and attitudes for 834 individual samples uncovered in literature searches and 7 large national data sets. In support of evolutionary psychology, results from both the individual studies and the large data sets indicated that men reported slightly more sexual experience and more permissive attitudes than women for most of the variables. However, as predicted by the gender similarities hypothesis, most gender differences in sexual attitudes and behaviors were small. Exceptions were masturbation incidence, pornography use, casual sex, and attitudes toward casual sex, which all yielded medium effect sizes in which male participants reported more sexual behavior or permissive attitudes than female participants. Most effect sizes reported in the current study were comparable to those reported in Oliver and Hyde's study. In support of cognitive social learning theory, year of publication moderated the magnitude of effect sizes, with gender differences for some aspects of sexuality increasing over time and others decreasing. As predicted by social structural theory, nations and ethnic groups with greater gender equity had smaller gender differences for some reported sexual behaviors than nations and ethnic groups with less gender equity. Gender differences decreased with age of the sample for some sexual behaviors and attitudes. (Contains 10 tables.)