Preventing the transmission of HIV, the virus that causes AIDS, is an important public health challenge. Researchers have sought to develop a microbicide--a substance to help users protect themselves against HIV. In the mid-1980s, researchers found that Nonoxynol-9 (N-9), a spermicide found in various contraceptive products, showed potential as a microbicide. However, more recent studies raised concerns that N-9 may increase certain users' risk of contracting HIV. GAO was asked to describe federal agencies' and contraceptive product manufacturers' actions related to N-9 and HIV. In this report, GAO reviewed (1) the efforts by federal agencies and manufacturers of contraceptive products to assess the safety of N-9 and its effectiveness as a microbicide for preventing HIV transmission and (2) the information provided to the public about the safety of N-9 and its effectiveness as a microbicide. GAO reviewed journal articles, Federal Register notices, product packaging, educational materials, and other documents. GAO also interviewed officials from the Centers for Disease Control and Prevention (CDC), the Food and Drug Administration (FDA), the National Institutes of Health (NIH), and selected manufacturers of N-9 contraceptive products.