Percutaneous transluminal coronary angioplasty (PTCA) has had complications related to dilating catheters and guide wires such as coronary artery dissection, spasm, rupture, and perforation. This report describes four patients who developed cardiac tamponade following PTCA, presumably from right ventricular (RV) perforation. All four received large doses of heparin during PTCA and three received antiplatelet therapy. In three cases, cardiac tamponade occurred several hours after PTCA. All patients did well following operative intervention and no patient required repair of a cardiac perforation. We postulate that impaired hemostasis in the presence of an otherwise inconsequential RV perforation causes tamponade. Three alternatives to provide standby pacing are proposed.