This article reviews what has been learned to date about the role of gender-based power in sexual relationships in determining sexual and reproductive health outcomes. A framework for assessing the relationship between power relations and reproductive health is outlined and measurement issues are critically discussed. A summary is included of the main types of intervention approaches that have been implemented, as are a discussion of the programmatic, methodological, and ethical implications of the findings and recommendations for further experimentation and research. Although many challenges remain, results to date suggest that when the role of gender-based power is made an integral feature of sexual and reproductive health programs, there is a considerable payoff for both women and men.