Purpose: To review and update the evidence relating to the personal, social, and environmental factors associated with physical activity (PA) in adults. Methods: Systematic review of the peer-reviewed literature to identify papers published between 1998 and 2000 with PA (and including exercise and exercise adherence). Qualitative reports or case studies were not included. Results: Thirty-eight new studies were located. Most confirmed the existence of factors already known to be correlates of PA. Changes in status were noted in relation to the influence of marital status, obesity, smoking, lack of time, past exercise behavior, and eight environmental variables. New studies were located which focused on previously understudied population groups such as minorities, middle and older aged adults, and the disabled. Conclusion: The newly reported studies tend to take a broader "ecological" approach to understanding the correlates of PA and are more focused on environmental factors. There remains a need to better understand environmental influences and the factors that influence different types of PA. As most of the work in this field still relies on cross-sectional studies, longitudinal and intervention studies will be required if causal relationships are to be inferred.