In this study, we compared the procedure-related complications of inpatient and outpatient cardiac catheterization when performed at the same institution by the same group of cardiologists. The majority of the studies were done using a brachial arterial cutdown approach. The mean age, sex, cardiac diagnosis, mean left ventricular ejection fraction, and the distribution of coronary arterial lesions were similar in both groups. There were relatively more patients in the New York Heart Association's class 4 in the inpatient group (p less than 0.01). In the outpatient group (676 patients), there were no major complications, and the rate of minor complications was 1 percent. In the inpatient group (1,106 patients), the rate of major complications was 0.4 percent and of minor complications 1.4 percent. The rates of major, minor, and total complications were statistically similar between the two groups. In the outpatient group the presence of left main coronary arterial disease, triple-vessel coronary disease, a left ventricular ejection fraction less than 30 percent, or a history of a recent myocardial infarction did not alter rates of complications. The hospital-related cost of the procedure on an outpatient basis was 26 percent less than on an inpatient basis. Our findings indicate that outpatient cardiac catheterization, using a brachial cutdown approach, is safe even in a higher risk subgroup of patients and provides significant financial savings.