Information about how appropriately procedures are performed is vital to the understanding of the impact of technology and to the success of efforts to channel its use appropriately. While the efficacy of coronary artery bypass surgery has been addressed in several large-scale, randomized trials, there is little information about how appropriately the procedure is actually being used in the community. We determined the appropriateness of coronary artery bypass surgeries performed in three randomly chosen hospitals in a western state. We determined appropriateness by comparing data obtained from a detailed medical record review with a list of 488 indications. This list, developed by a national panel of physicians, covered all possible reasons for performing the procedure. Three hundred eighty-six cases from the years 1979, 1980, and 1982 were examined. Fifty-six percent of the surgeries were performed for appropriate reasons, 30% for equivocal reasons, and 14% for inappropriate reasons. The percentage of appropriate surgeries varied by hospital, from 37% to 78%, but did not vary by patient age. Eliminating the performance of inappropriate procedures may lead to reductions in health care expenditures or to improved patient outcomes.