PURPOSE: To determine whether teaching medical students has concurrent economic effects on physicians and their practices. METHOD: The authors reviewed 869 patient-encounter forms completed in April 1994 and July 1995 by four family medicine physicians who were clinical faculty at the State University of New York Health Science Center at Syracuse. The authors compared those forms that were completed when a third-year medical student was present for the patient encounter with those completed when a student was not present. The authors looked for differences in the distributions of billing codes and in the frequencies of in-office procedures performed and diagnostic tests ordered. RESULTS: The presence or absence of a third-year medical student had no significant effect on the variables studied. CONCLUSION: In the clinical settings studied, concurrent medical student teaching did not appear to affect the distribution of billing codes or the frequency of in-office procedures performed or diagnostic tests ordered.