There is increasing recognition that the elevated prevalence rates of cocaine and methamphetamine use among men who have sex with men (MSM) are key drivers of the HIV/AIDS epidemic in this population. Because stimulant use and HIV/AIDS are intertwined epidemics, investigations that examine the psychological correlates of stimulant use among MSM can inform the development of innovative HIV/AIDS prevention interventions. In the limited number of studies conducted to date, psychological correlates of stimulant use have been examined almost exclusively in convenience samples of active methamphetamine users. Further research with more representative samples of MSM is needed to determine whether psychological vulnerabilities differentiate between active stimulant users and non-users. The proposed study will utilize extant data from the Urban Men's Health Study III, a probability-based survey of 879 MSM in San Francisco. These data provide a unique, cost-effective opportunity to examine psychological correlates of stimulant use among MSM who were recruited through probability-based sampling methods. Informed by Stress and Coping Theory, the proposed study will utilize structural equation modeling to examine psychological correlates of engaging in any stimulant use during the past 6 months with 711 MSM who completed a mail-in questionnaire that assessed psychological factors and substance use. By advancing our basic understanding of stress and coping processes that may promote engagement in stimulant use, the proposed study will inform the development of innovative interventions to prevent stimulant use or decrease the frequency of stimulant use among MSM. The proposed study addresses a critical public health issue facing men who have sex with men (MSM). By identifying psychological factors that differentiate between active stimulant users and non-users, the proposed study will inform the development of innovative stress and coping interventions designed to prevent stimulant use or reduce the frequency of stimulant use among MSM. Reducing stimulant use in this population could ultimately alleviate human suffering related to substance abuse as well as decrease HIV transmission rates.