The relationship between various forms of nonreproduction (especially homosexuality) and intelligence (as measured by IQ and other tests) is investigated by a systematic review of the literature, selecting studies without regard to the direction of their findings. Most studies found the more homosexual subject groups' scores to be higher than those of the more heterosexual controls, and all exceptions to this trend are concentrated in one subgroup: prisoners. Moreover, the more representative the sample studied, and the less subject to challenge the methodology used, the clearer and more statistically significant was the superiority in intelligence of the more homosexual over the more heterosexual group.