Transactional sex, or the exchange of money and gifts for sexual activities within nonmarital relationships, has been widely considered a contributing factor to the disproportionate prevalence of HIV/AIDS among young women in sub-Saharan Africa. This study applied social exchange theory to premarital relationships in order to investigate the linkages between a variety of young women's resources--including employment and material transfers from male partners--and sexual behaviors. Data on the first month of premarital relationships (N = 551 relationships) were collected from a random sample of young adult women ages 18-24 in Kisumu, Kenya, using a retrospective life history calendar. Consistent with the hypotheses, results showed that young women's income increases the likelihood of safer sexual activities, including delaying sex and using condoms consistently. Material transfers from the male partner displayed the opposite effect, supporting the view that resources obtained within the relationship decrease young women's negotiating power.