The frequency and outcome of emergency CABG for complications of PTCA in the NHLBI PTCA Registry were analyzed. Emergency surgery was performed in 202 patients (6.6%). The most frequent indications for emergency operation were coronary dissection in 46%, coronary occlusion in 20%, prolonged angina in 14% and coronary spasm in 11%. Emergency surgery was most often necessary in patients in whom lesions could not be reached or traversed, but more than 25% of patients who required emergency surgery had initially successful dilatation followed by abrupt reclosure of the vessel. The mortality rate with emergency CABG was 6.4%, and nonfatal MI occurred in 41% of patients, with Q waves developing in approximately 60% of patients with MI. However, 53% of patients managed with emergency CABG for severe ischemic events with PTCA did not have evidence of MI or die and had an uncomplicated postoperative course. No baseline clinical predictors of emergency surgery were identified. Lesion eccentricity was associated with a significant increase in frequency of emergency operation, and the incidence of emergency surgery declined with increasing experience with PTCA.