Only 25 percent of Americans participate in recommended levels of physical activity, despite the health benefits associated with physical activity. Physical activity promotion is an important public health issue. Several research studies indicate that physical activity interventions using theoretical frameworks such as the Stages of Motivational Readiness for Change Model (SOC) increase physical activity behavior among sedentary adults. The SOC Model posits that different intervention strategies should be applied depending upon the individual's current stage of readiness for change. The first section of this digest presents an overview of the SOC, in which individuals move through a series of stages as they adopt and maintain a new habit. The second section examines the efficacy of the SOC, focusing on targeted interventions; tailored interventions; delivering a stage-targeted intervention (precontemplation, contemplation, preparation, action, and maintenance); tailoring the intervention to the individual; and delivery channels and settings. The brief concludes that physical activity interventions based on the SOC Model have been shown to increase physical activity behavior among adults, and it can be applied in a variety of settings (Contains 39 references.) (SM)