In industrialized nations like the United States and Sweden, the vast majority of adults do not meet the physical activity guidelines of 150 minutes per week.1 Inactive lifestyles put most adults at risk of cardiovascular diseases (CVD), diabetes, obesity, some cancers, osteoporosis, and psychological disorders.2 Physical activity can be effective at all phases of chronic disease management, from primordial prevention (prevention of risk factors) through treatment and rehabilitation.2 There is particular interest in the potential for physical activity to prevent chronic diseases, thereby improving quality of life and reducing health care costs.3 In the past decade, limitations of prevention approaches that target mainly individuals with educational and motivational programs have been recognized, triggering a trend to consider influences on behavior that are outside the person, such as the built environment.4,5 The purposes of the present paper are to describe multilevel ecological models of behavior as they apply to physical activity, describe key concepts, summarize evidence on the relation of built environment attributes to physical activity and obesity, and provide recommendations for built environment changes that could increase physical activity. The intent of this non-systematic review is to present conclusions from previous reviews then illustrate results by highlighting selected studies.