Coronary perforation is a rare, but potentially catastrophic, complication of percutaneous coronary intervention. A retrospective review of the Cardiology Quality Assurance Database was performed for all percutaneous coronary interventions (n = 8,932) at William Beaumont Hospital from October 1988 to December 1992. Coronary artery perforation was reported in 35 patients (0.4%0), including after percutaneous transluminal coronary angioplasty (PTCA, 11/7,905,0.14%), transluminal extraction coronary atherectomy (TEC, 6/420, 1.3%), directional coronary atherectomy (DCA, 1/249, 0.25%), and excimer laser coronary angioplasty (ELCA, 5/242,2%); and none after high-speed mechanical rotational atherectomy with the Rotablator (MRA, 0/116, OYO). Perforations were classified by coronary angiography as free perforations (n = lo), contained perforations (n = 17), or other types of perforation (n = 8). Although perforation was apparent in 32 (91%) of 35 angiograms, delayed cardiac tamponade occurred in 3 patients (9%0), despite the absence of angiographic evidence for perforation at the time of the procedure. Causes of perforation were the guidewire in 7 (20%), an interventional device in 26 (74%), and indeterminate in 2 (670). Complex B, or C lesions accounted for 83% of perforations. Final treatment included conservative therapy (reversal of anticoagulation and/or PTCA) in 22 (63%) and surgical intervention (with or without bypass surgery) in 13 (37%). Serious clinical complications included cardiac tamponade in 6 (17%0), blood transfusion in 12 (a%), myocardial infarction in 9 (26%), and death in 3 (9%).