In Brazil, as in other Latin American countries, there was a sharp increase in the number of medical schools in the past 20 years. The result was a steep increase in the number of physicians. These professionals are in many cases, however, poorly trained. As a consequence, public, as well as private health services, are exposed to professionals of great diversity of qualification. Few effective solutions have been proposed for this health services management problem. This paper presents a potential solution. It exposes preliminary results of field tests of an Expert System based on the first author's (Rozenbojm) three decades of experiences as a clinician, and medical residency advisor. The system was developed using ESE IBM Expert Systems language and a mainframe hardware. It was designed to support diagnosis based only in anamnesis and physical examination data, without lab or X ray support. Its original purpose was to increase the primary care physician's diagnostic and therapeutic accuracy. An initial test with specialist panels (endocrinology, cardiology, nephrology, G.O., gastroenterology, pediatrics and pneumology) revealed spell out a diagnostic and therapeutic concordance rate over 95 percent (based on real everyday practice cases brought by the specialists). A second test was performed in a private Health Care Network, at primary care level. In this case, concordance rate was over 83 percent in diagnostic aspects and 95 percent in the clinical orientation aspects. This expert system may be very useful for Health Services providing, first encounter standardization, medical graduate basic education and cost containment. The next proposed steps includes transcription of the software for personal computer utilization and an evaluation of its economic impacts.