This article examines the quality of acute episodic care for five diagnostic categories amenable to one-visit diagnosis and treatment at the nation's largest chain of investor-owned ambulatory care centers. A total of 803 medical records were audited for five common conditions and measured against specific protocols. In four of the five diagnostic categories studied--pharyngitis, otitis media, vaginitis, and use of tetanus immunization--42-97% of patients received care that met or exceeded the standards set by a panel of practicing academic physicians. In follow-up of an incidental high blood pressure reading, however, study physicians met the standard only 24% of the time. Some overprescribing and overtreatment with immunizations were detected. As far as comparison is possible to other studies, results suggest that care in this setting falls within the range of experience that has been reported for other types of practices. In spite of direct economic incentives to increase volume, little evidence was found of overuse of ancillary tests or unnecessary scheduling of repeat visits.