It has been suggested that coronary artery bypass grafting (CABG) is efficacious in patients with severe coronary artery disease before they undergo a major noncardiac operation. The Coronary Artery Surgery Study (CASS) registry population was reviewed to identify variables affecting operative mortality and cardiovascular morbidity for noncardiac procedures, and to assess the influence of prior CABG on these surgical risks. Major noncardiac operations were performed on 1,600 registry patients between June 30, 1978, and June 30, 1981. Operative mortality for individuals without significant coronary artery disease (Group 1) was 0.5% (2/399) and for patients with such disease having CABG prior to a noncardiac procedure (Group 2), it was 0.9% (7/743) (Group 1 versus Group 2, p = 0.42). Patients with significant coronary artery disease undergoing noncardiac operation without prior CABG (Group 3) had an increased operative mortality, 2.4% (11/458) (p = 0.009). Group 2 patients had more severe angina symptoms (p less than 0.001) and more extensive coronary artery disease (p less than 0.001) on entering CASS than Group 3 patients. Postoperative chest pain occurred in 8.7% (40/458) of the Group 3 patients versus 4.5% (18/399) in Group 1 and 5.1% (38/743) in Group 2 (p = 0.004). No group differences were noted for the incidence of perioperative myocardial infarction or arrhythmias.(ABSTRACT TRUNCATED AT 250 WORDS)