Increasing evidence suggests that physical inactivity is a prime contributor to poor health, poor functioning, and diminished well-being in older adults. This in turn leads to increased likelihood of use of health care services and institutionalization. Strategies to preserve and enhance the physical capabilities of older people may thus provide major health and cost-saving benefits. We propose a 3-year project to implement and evaluate a program to increase the physical activity levels of noninstitutionalized older adults. The program makes use of the many existing physical activity classes in the community (Palo Alto, California). This feature minimizes program costs, enables people to continue their new activities beyond the grant period, and facilitates the program's transferability to other communities. The program will be targeted to all residents in two similar community senior housing facilities in Palo Alto. The program, which is based on social learning and related approaches to intervention, focuses on encouraging participants to initiate and maintain higher levels of physical activity through increased utilization of already available community programs. The intervention will include group sessions, individual counseling, peer advocates, partnering participants with others interested in the same activities, and environmental strategies to enhance participation. It also includes community-level strategies such as the use of media and physician recommendations to become more active. In phase L the 6-month program will be implemented in one facility (N= 120) with the second facility serving as a comparison group (N=80). Evaluation of the program will be based on a comparison of these two groups using a quasi-experimental design. Primary outcomes of the evaluation are participation in physical activity classes and more general levels Of physical activity. Secondary outcomes focus on a comprehensive profile of functioning and well-being. In Phase II, the ability of participants in the experimental group to maintain physical activity levels after the program ends will be evaluated for a second 6-month period, and the replicability of the program will be tested in the second facility. Our goal is to develop a model for community-based and community-sustained programs to help older adults utilize existing fitness resources and maintain interest and participation in those programs at a level sufficient to obtain desirable health benefits.