A longitudinal study of patients with chronic medical diseases (hypertension, diabetes, heart disease) was conducted to identify antecedents of adherence to medical recommendations. Data are from 1198 patients in three health-care provision systems in Los Angeles, Chicago, and Boston. Nonadherence at the beginning of the study was the strongest predictor of nonadherence 2 years later. Other significant predictors varied by type of adherence outcome. Patients who were younger and who relied upon avoidant coping strategies tended to be less likely to follow their doctor's specific recommendations. Patients who were distressed about their health, used avoidant coping strategies, or who reported worse physical and role functioning were less likely to adhere in general. Patient satisfaction with two features of care (interpersonal quality and financial aspects) was positively related to adherence in some models, but satisfaction with the technical quality of care was negatively associated with adherence to specific recommendations among heart disease patients. Social support contributed to specific adherence among diabetic patients. Implications of the study for medical care providers are discussed.