Introduction. Recent reports have linked the use of phosphodiesterase type 5 (PDE-5) inhibitors with increased rates of high-risk sexual behavior and HIV transmission in some individuals. Aim. A National Institute of Mental Health (NIMH)-funded, multidisciplinary conference was convened to evaluate scientific research, clinical and ethical considerations, and public policy implications of this topic. Main Outcome Measures. Published and unpublished findings on effects of PDE-5 inhibitors on sexual behavior; published guidelines and management recommendations. Methods. Leading investigators in relevant disciplines (e.g., public health, epidemiology, medical ethics, urology, psychology) participated in a 2-day meeting, including representatives of government, scientific, and regulatory agencies (the Centers for Disease Control, Food and Drug Administration, NIMH, and the National Institute on Drug Abuse). Panelists provided critical reviews of substantive areas of research, followed by question and answer sessions on each topic. On the second day, working groups were convened to identify critical gaps and priorities in three major areas: (i) research and evaluation needs; (ii) prevention strategies and clinical management issues; and (iii) policy and prevention implications. Results. Research needs and priorities were categorized into four specific areas: (i) basic and clinical/laboratory research; (ii) epidemiology and risk factors; (iii) social-behavioral processes and interventions; and (iv) prevention/policy and educational needs. Identified gaps in the available data include populations at risk (e.g., risk among heterosexuals, risk profiles among subpopulations of men who have sex with men) and the specific role of PDE-5 inhibitors in HIV seroconversion. Specific areas of emphasis were the need for safer sex counseling, comprehensive sexually transmitted infection (STI) screening and follow-up when indicated, avoidance of potentially dangerous drug interactions, and potential benefits of testosterone replacement for HIV-positive men with decreased androgen and other symptoms of hypogonadism. Conclusions. A conference was convened on the topic of PDE-5 inhibition and HIV risk. This "white paper" summarizes the findings of the conference and recommendations for future research.