Topical vaginal microbicides are being developed to reduce HIV infection in women for whom correct and consistent condom use is impossible or undesirable. Although microbicides have been heralded as a "women-initiated" method that requires no action of the male partner, gender norms for sexual relationships and sexual practices could impede acceptability and use. To facilitate development of microbicides and look ahead to their eventual introduction, it is necessary to understand couples' sexual dynamics, including power and pleasure. This article presents data from a study of microbicide acceptability ancillary to a microbicide clinical trial in Malawi and Zimbabwe. Female trial participants, male partners, health care professionals and community stakeholders were interviewed about norms for sexual decision-making, sexual pleasure, and associated intravaginal practices that ensure this pleasure. Even though acceptability of microbicides was found to be high, sexual intercourse is accompanied by issues of power and gender norms that place women, particularly those in stable union, at a disadvantage for enactment of risk reduction strategies. Although woman-initiated use is an important goal in development of microbicides, the need for men's cooperation or agreement must be addressed in strategies for future product introduction.