Compliance is an ancient topic subjected to intense recent scrutiny as a result of scientific and social changes which focus on lifestyle adjustment to chronic illness and emphasize increasing patient involvement in self-care. Difficulties in definition, measurement and research design as well as the complexity of the problems contribute to conflicting findings and a lack of consensus about determinants of compliance. Five conceptual models have been studied but only a few positive and negative factors have been consistently identified, perhaps because outcome is often influenced by subtle attitudes, beliefs and quality of life considerations. Management involves both education and a variety of interventions that range from simple single strategies to complex multimodal approaches in which the patient's role may vary from being a passive participant of professional supervision to complete autonomy and self-care.