Although the results of quantitative studies often indicate that students of male teachers perform worse on achievement tests than those of female teachers, it is not clear that men are less effective teachers. Instead, male teachers may work in more difficult environments. This study uses longitudinal data from Mexico's national teacher incentive program to examine the effectiveness and distribution of male teachers in two Mexican states. While we find some evidence that the students of male teachers score lower than those of female teachers, we also find that male teachers are disproportionately concentrated in lower-achieving and rural schools, and in higher-poverty municipalities. (Contains 3 tables.)