The cost of hospitalization required for cardiac catheterization led us to evaluate this procedure in 308 adult outpatients. Patients wee scheduled on the basis of stability of symptoms. Two hundred eighty-eight underwent left heart catheterizations and coronary arteriography. Ninety-five percent of the procedures were performed by the percutaneous technique. Fifty patients had normal studies and 30 patients had congenital or valvular disease. Two hundred twenty-eight patients had significant coronary artery disease, 85 patients had triple vessel disease, and 45 patients had left main coronary artery disease. There were six significant complications: one death; two myocardial infarctions; one air embolism, and two patients with hematomas. Three of the complications were in patients with left main disease. Only two of the complications can be ascribed to the outpatient nature of the procedure. The complication rate is comparable to that reported in the literature. Fifteen hundred subsequent cases were studied as outpatients, with a very low mortality and morbidity. It is concluded that cardiac catheterization can be performed on an outpatient basis with safety comparable to inpatient studies, and at a great economic savings.