In an effort to uncover useful directions for future research, this paper examines the cross-cultural data on male homosexuality in light of various theories that might account for its variation. Looking first at different psychological explanations, the study suggests that the sex of one's childhood companions may be an important factor in the origin of homosexuality. Two possible explanations for an association between male homosexuality and mixed-sex playgroups are offered: In one, gender identity serves as an intervening variable; in the other, the notion that "familiarity breeds contempt" is studied. A cultural materialist theory, which views homosexuality as adaptive under conditions of population pressure, is shown to be supported by the correlation between a society's natalist policy and its attitudes toward homosexuality.