Biological and social-experiential factors appear to play a role in the male advantage in spatial abilities. In the present study, relations among prenatal testosterone levels, spatial play experiences, and mental rotation task performance were explored in 7-year-old boys and girls. A positive correlation was observed between prenatal testosterone levels and rate of rotation in girls. The findings were less clear for boys, but suggested the opposite pattern of results. Relations between spatial play preferences and mental rotation task performance were not observed in children of either sex. These findings are consistent with the hypothesis that testosterone acts on the fetal brain to influence the development of spatial ability.