Performed a meta-analysis of 100 studies of gender differences in mathematics performance. They yielded 254 independent effect sizes, representing the testing of 3,175,188 Ss. Averaged overall effect sizes based on samples of the general population indicated that females outperformed males by only a negligible amount. An examination of age trends indicated that girls showed a slight superiority in computation in elementary school and middle school. There were no gender differences in problem solving in elementary or middle school; differences favoring men (...) emerged in high school and college. Gender differences were smallest and actually favored females in samples of the general population, grew larger with increasingly selective samples, and were largest for highly selected samples and samples of highly precocious persons. The magnitude of the gender difference has declined over the years. Gender differences in mathematics performance are small. Nonetheless, the lower performance of women in problem solving that is evident in high school requires attention. (shrink)