To investigate whether the process of graduate medical education increases costs in teaching hospitals by causing longer lengths of stay and greater resource use, we compared lengths of stay, hospital charges, and the use of cardiovascular procedures for patients with acute myocardial infarction admitted to the teaching and nonteaching services of a university-affiliated community hospital.After adjusting for severity of illness and demographic characteristics, patients on the teaching services had a mean length of stay that was shorter by 0.6 days (p = 0.04) and mean charges that were $2,060 lower (p = 0.15) than for patients on the nonteaching service. Patients on the teaching service also had 15 percent (95% CI: -26, -4) fewer cardiac catheterizations and 9 percent (-18, 0) fewer