Continuity of care is of value only to the extent that it has an impact on the outcome of care, the prevention or reduction of physical, mental, or social disabilities, the satisfaction of patients, and the costs of care. It is important that research studies include patients with a broad range of social characteristics and that costs as well as health care benefits be measured. An accountability model describing the contributions of physicians, health care institutions, patients, and the local community to health outcomes is recommended. The following three principles are outlined for the evaluation of health care: (1) determine the patient's health status before and after care, (2) use appropriate measures of health outcomes, and (3) consider potential effects of factors extrinsic to medical care.