Utilizing a quality assessment methodology for ambulatory patient care currently under development by the Indian Health Service's (IHS) Office of Research and Development, comparisons were made between results derived from a pilot test in IHS service units, 2 metropolitan Health Maintenance Organizations (HMO), and 3 rural private practices. Comparison of the systems' performances were made for the following tracer conditions: prenatal care; infant care; streptococcal; urinary tract infection; lacerations of scalp and extremities; hypertension; and iron-deficiency anemia. Results indicated: no substantial and consistant difference in the performance of the providers of care; observable differences attributable to patient contact with the system of care or system recognition of the need for service; IHS provided more widespread application of counseling and educational tasks and selected screening tasks, had higher patient contacts, and had lower recognition of the need for service than private practices or HMO's; private practices and HMO's had higher recognition of service need and higher follow-up rates than IHS; private practices had somewhat of a higher follow-up rate than the HMO's; HMO's had a somewhat higher application rate for counseling, education, and health surveillance tasks than private practices. Since the provider indicators did not reveal a particularly high level of performance, it was concluded that systems performance could be substantially improved if all practices capitalized upon existing patient visit patterns. (JC)