With the advancement of coronary arterial surgery over the last decade, cardiac catheterization and coronary angiography have become frequently performed diagnostic procedures. Previously, the usual policy was to admit the patient to the hospital one day prior to the study, followed by overnight observation after the cardiac catheterization. The increase in the number of studies performed and the ever-escalating cost of hospitalization have prompted some institutions to evaluate the safety of outpatient cardiac catheterization and coronary angiography. These studies examine the rates of complications in relatively small numbers of outpatients and do not report on the procedure-related complications of inpatient cardiac catheterization in the same institutions. We initiated this study to compare rates of complications of outpatient and inpatient cardiac catheterization when performed in the same institution by the same group of cardiologists.