The promotion of physical activity in older populations holds the promise of promoting health and reducing the risk of disablement. Individual- and community-based programs are often presented as being distinct and, in some cases, antithetical. The objective of this paper is to illustrate, through the use of an ecologic model, that individual- and community-based programs are complementary. The following topics are discussed: (1). the development of transdisciplinary theories; (2). the establishment of better measures to address the linkages across individual behavior, group behavior, the built environment, and the temporal sequence of biological, behavioral, and environmental factors; (3). the translation of research into practice and policies; and (4). the training of a new generation of scholars and practitioners to develop and execute research, practice, and policy agendas in this area. An ecologic model fosters a comprehensive agenda based on biological, behavioral, and environmental factors. The study of the interaction of the individual with the environment is challenging but potentially more important than the study of the role of the individual or the environment alone in the promotion of physical activity.