Contemporary feminist theory has moved into posthuman terrains as feminist theorists utilise human/nonhuman relations and a motley crew of nonhuman entities to reinvigorate feminist critique of nature/culture dichotomies. But what place is left for sex/gender relations in this move beyond the human? Materialities of Sex in a Time of HIV is written on the cusp of feminist theory of materiality and the analysis of an object at the heart of various sex/gender manifestations - the vaginal microbicide. Vaginal microbicides are female-initiated HIV prevention methods (currently tested in clinical trials) designed as creams, rings, gels and sponges that women can insert vaginally before having sex to protect themselves against HIV infection. The microbicide is developed as a tool for women's empowerment in the HIV epidemic, but what happens to feminist ideals when they materialise through biomedical practice? This book provides an analysis of the field of microbicide development to articulate the complexity of its promise and material effects; and utilises the microbicide as an analytical ally in a provocative debate with contemporary feminist theory.