As the number of aged persons in the population grows, it is important to identifyand understand those lifestyle components that contribute to an improved quality of lifeand maintenance of functional independence. Benefits of regular physical activity includereduced risk for diabetes, obesity, cardiovascular disease, cognitive dysfunction, andother physical and psychological health outcomes [Rejeski et al., 2002; Taylor et al.,2004; Weinstein et al., 2004; Kramer et al., 2003; McAuley, Kramer, & Colcombe,2004]. Despite these benefits, a large proportion of adults fail to engage in any physicalactivity [United States Department of Health and Human Services (USDHHS), 2000]with women, the elderly, and minority populations reporting the greatest levels ofinactivity.Increasingly, links between elements of the built/physical environment and physicalactivity are being examined. One potentially useful approach to understanding physicalactivity behavior is through the use of ecologic models [Berrigan & Troiano, 2002]. Anecologic model examines both environmental and individual determinants of behavior,conceding both direct and indirect influences of each on behavior, and the tendency oftheir respective influences to shift over time. Individual characteristics interact withbehavior, and both are influenced by the social and physical environments in areciprocally determining manner; contributing to overall health. This triadic form ofreciprocal determinism is central to Bandura's social cognitive theory [Bandura, 1986,1997]. To date, very few studies have utilized transdisciplinary theories and researchdesigns to determine the utility of individual and environmental interactions in predictingphysical activity [Li, Fisher, Brownson, & Bosworth, 2005; Satariano & McAuley, 2003;King, Stokols, Talen, Brasington, & Killingsworth, 2002]. Consequently, there existnumerous conceptual, theoretical, and definitional ambiguities associated with thisliterature. This chapter provides a critical review of the literature on physical activity and theenvironment in older adults. Specifically, attention is given to the large degree ofvariability that exists in the operationalization of common environmental characteristics(e.g., population density, access to recreational facilities, land-use mix) as well asphysical activity behavior (e.g., step counts, self-report activity behavior, walking fortransport) and how these different viewpoints influence the types of outcomes assessedand the measurement tools utilized. Moreover, the role of theory in the design andimplementation of research into the environment-behavior relationship and directions forfuture research are discussed. © 2010 Nova Science Publishers, Inc. All rights reserved.