A case of perforation of the left ventricle during selective cineangiocardiography in a 27-month-old child with aortic stenosis is reported. Perforation was visualized during the power injection, and subsequent cardiac tamponade developed. Immediate pericardiocentesis resulted in rapid improvement and the child made an uneventful recovery. At cardiac surgery for aortic valvotomy 5 days later no abnormalities of the pericardium were noted but there was a small area of discoloration on the posterior left ventricular free wall. Prevention of poor catheter positioning is suggested as the major preventive measure to avoid such complications during selective ventricular angiocardiography.