The overall goal of this program is to elucidate the impact of HIV infection on nutritional status and functional capacity of the host. Three projects are proposed in this revised application: 1. A longitudinal nutrition survey conducted in Boston and Baltimore which measures dietary intake, body composition, biochemical and immunological markers, GI function, state of energy metabolism, and quality of life indicators; 2. A study of muscle physiology, cytokine production and protein metabolism in response to acute exercise stress. In addition, a program of exercise training will be evaluated for restoration of muscle mass and strength; and 3. A study of longitudinal nutritional survey and intervention studies in HIV-infected infants and children. The choice of research topics is based on their perceived importance to the general problem of nutrition and HIV infection, the limited, or in some cases controversial, data on the topic, and the expertise of our group. These studies are supported by four cores: administrative, biostatistical/data management, biochemistry, and dietary assessment/body composition. The project will enroll HIV-positive persons at all stages of disease; however, special emphasis will be placed on the early asymptomatic phases in order to identify the premonitory signs of weight loss and nutritional deficits. The recruitment of underserved and poorly studied populations, such as women, minorities and children, will receive a high priority. Through these studies we hope to understand the nutritional deficits in HIV infection, particularly in the early phases when interventions might have a salutatory impact.