Pediatric cardiac catheterization may be indicated under certain conditions, but is associated with some risk. The purpose of the study was to evaluate the complications associated with diagnostic and interventional catheterization procedures done over an 18-month period in our laboratory. Of the 230 cardiac catheterizations, 204 were solely diagnostic in nature. Eleven percent were interventional catheterizations including aortic and pulmonary valvuloplasties and balloon atrial septostomy. Six percent of the patients constituted grown-up congenital heart disease (GUCH). The median age was 34 months excluding the GUCH group. There was one death below one year of age (0.4% mortality) occurring six hours after the diagnostic catheterization; it was attributed to the underlying disease. There were eight complications (3.4%) that we would consider serious, including atrial flutter, ventricular tachycardia, severe hypercyanotic spell, seizure, transient complete heart block, peripheral vascular injury which resulted in pseudoaneurysm formation of the femoral artery requiring surgical intervention, and transient pulse loss. When catheterization is necessary, it should be carried out as efficiently as possible with awareness of conditions that probably increase the risk of a clinically important event. Although patients undergoing cardiac catheterization are now younger and have more complex cardiac abnormalities, the procedure seems to have become safer when compared to previous literature.