The settings in which health care services are delivered have the potential to influence the quality of health care services in numerous ways, but little is known about the relationship between characteristics of medical practices and quality of care. In this study, the authors studied patients with coronary heart disease (CHD). The authors surveyed 225 medical practices in 2000 and 2001 and obtained information on quality measures from the medical records for more than 1,600 of their patients with CHD. Results suggest that quality of care, at least for common conditions with agreed-on measures, is not strongly influenced by financial characteristics of medical practices, although there does seem to be some relationship with practice structure such as size and quality.