As additional persons become infected with human immunodeficiency virus (HIV) an mortality due to this infection declines, more drug users and others with HIV infection will live to experience co-morbid conditions associated with aging. Some of these conditions appear likely to occur more commonly or to be more severe in persons with HIV infection, as a direct result of HIV infection or complications of its treatment. Presently there is little known about the possible effects of HIV infection and its treatments on diseases of aging in current or former drug users or other aging individuals. Prominent among such disorders commonly affecting older individuals are atherosclerotic disease and osteoporosis. To address these issues, we will conduct a five-year prospective study of aging, atherosclerosis, bone mass loss, and drug use in men 50 years or older with or at risk for HIV infection in the Bronx, New York City. A cohort of current or former drug users will be recruited from a longitudinal study, the Bronx HERO (HIV Epidemiological Research on Outcomes) Study, and from substance abuse treatment programs, other clinical care sites at our institutions, and the surrounding community. We will take advantage of an ongoing longitudinal study of older women drug users and other women with or at risk for HIV infection that is using similar methodology, in order to assess the role of gender on these conditions. The specific aims of the project are to: 1. Determine the effect of HIV infection and highly active antiretroviral therapy (HAART) on the rate and risk factors for atherosclerotic disease. Among risk factors to be considered will be dyslipidemia, insulin resistance, obesity, diet, and medication and illicit drug and alcohol use. 2. Determine the effect of HIV infection and HAART on age-related loss of bone mass. 3. Determine the effect of HIV infection and HAART on high-risk drug using and sexual behaviors of older men. 4. Take advantage of an ongoing study of a cohort of older women, which addresses similar issues using comparable methodology, in order to compare atherosclerosis, bone loss, and drug use and sexual behaviors in men and women.