Accumulating evidence links partner violence and HIV infection. Among the groups disproportionately affected by these trends are methadone patients. Estimated lifetime rates of partner violence reported by women in drug treatment programs range from 60% to 75%. Seroprevalance rates of HIV among methadone patients in East Coast urban areas range from 28% to 43%. Despite the high prevalence of partner violence and HIV among methadone patients and mounting evidence suggesting that partner violence and HIV-risk behaviors may be interrelated phenomena in this population, studies have yet to untangle the multi-dimensional relationship between these two critical public health problems. Moreover, as of yet, no empirical research has examined these relationships from the male perpetrator's perspective. Longitudinal data on the bi-directional relationships between the perpetration of partner violence and HIV-risk behaviors among men on methadone may address some of the major gaps in research. The proposed study will: 1) explore the relationship dynamics and sequences of events that culminate in the co- occurrence of inflicting partner violence and engaging in HIV-risk behaviors among men who are enrolled in methadone maintenance treatment programs (MMTPs) using in-depth qualitative methods; and 2) examine longitudinally the relationships between the perpetration of partner violence and HIV-risk behaviors among men in MMTPs, controlling for background variables and risk factors (e.g., drug use, communications, prevalence of violence in perpetrator's social network). In the beginning of the first year, men attending MMTPs who report perpetrating partner violence in the past year will participate in focus groups (n=64) and in-depth interviews (n=50) for the longitudinal study that will begin in the second year, 600 men will be interviewed at baseline and at six and twelve month follow-ups. At the completion of the longitudinal study, two focus groups will be conducted with 16 men who report perpetrating partner violence in the part year, to elicit their interpretation of the quantitative research findings. Subjects will be recruited from Beth Israel Medical Center methadone clinics in Harlem. This study will be led by investigators from the Social Intervention Group (SIG) at Columbia University School of Social Work and Beth Israel Medical Center. Data from the proposed study will help inform assessment, treatment and referral protocols to reduce partner violence and HIV-risk behaviors among men and women in MMTPs.