Ronald Stall, Ph.D., M.P.H., has conducted research on the intersections between substance use and HIV infection since the early 1980's. He wrote the first paper demonstrating an association between substance use and high risk sex, wrote the first population-based paper describing the epidemiology of drug and alcohol use and abuse among gay men, directed the first intervention study to reduce high risk sexual behavior among substance abusing gay men (the 18th Street Study), co-authored the first paper demonstrating a predictive effect of drug use (and specifically, meth use) on HIV seroconversion among gay men, and authored the first paper describing the epidemiology of drug and alcohol use and abuse, as well as the independent associations of abusive patterns, within a "national" sample of MSM (the Urban Men's Health Study). Dr. Stall has served as PI or co-PI on numerous NIH grants studying the effects of alcohol and drug abuse on the unfolding HIV epidemic among gay men and other populations. He is currently working with a set of MACS collaborators to study the predictive effect of meth use on HIV risk-taking and HIV seroconversion, as well as other health outcomes. Dr. Stall has published over 100 peer-reviewed papers, the majority related to studies of sexual transmission of HIV among MSM and substance abusers. Prior to his current position at U. Pitt., he was the Branch Chief at the CDC’s Prevention Research Branch in the Division of HIV/AIDS Prevention.