Chemical barriers which can be controlled by the receptive partner to prevent transmission of HIV and other sexually transmitted diseases (STDs) are among the highest priorities for research and development. Advantage 24 is a contraceptive gel containing nonoxynol-9 (N-9). This study provides information on the safety of N-9 in a bioadhesive gel formulated for use by MSM during anal intercourse. Safety is assessed for both HIV-positive and HIV-negative men because HIV-positive men may be at increased risk for toxicity due to other HIV-related conditions.