To enhance our understanding of exercise adherence, predictors of adherence based on social-cognitive theory were compared with those derived from a trait approach. A community-based sample of older, sedentary men and women was administered the Self-Motivation Inventory and a self-efficacy questionnaire. Subjects were randomly assigned to one of three exercise regimens or to an assessment-only control condition for the following year. The subjects in the exercise conditions recorded each bout of exercise and rated the experience in terms of perceived exertion, enjoyment, and convenience (PEEC) on monthly logs. Based on social-cognitive theory, it was postulated that self-efficacy and certain aspects of the exercise bout itself, such as PEEC, would influence exercise adherence more than the general trait of self-motivation. Self-efficacy was significantly associated with exercise adherence at both 6 months and 1 year (rs = .42 and .44, respectively); self-motivation was not. Contrary to expectations, the PEEC components measured during the first 6 months did not make a significant contribution to the variance in adherence during the second 6 months.