Retrospective analysis of preoperative angiograms was conducted to determine potential candidacy for PTCA among the NHLBI Coronary Artery Surgery Study (CASS) Registry population undergoing initial and repeat CABG. Conservative criteria believed to be universally acceptable for PTCA were used. Patients were considered potential PTCA candidates if: (1) CABG had been performed to only 1 coronary artery system; (2) the critical disease was localized to the most proximal segment of that coronary artery system; (3) all distal segments of that coronary artery system were free of critical disease; and (4) the morphologic characteristics of the obstructing lesion were discrete and isolated. Left main CAD was excluded. Among persons who underwent initial CABG, 2.8% (261 of 9,369) were PTCA candidates, and 7.1% (20 of 283) of those who underwent repeat CABG were considered suitable for PTCA. The operative mortality risk of the PTCA candidates who underwent initial CABG was 0.4% (1 of 261). No PTCA candidates died during repeat CABG. Perioperative MI occurred in 2.3% (6 of 261) of the PTCA candidates who had initial CABG; none occurred among those who underwent repeat surgery. Total surgical complications occurred in 15.7% (41 of 261) of the PTCA candidates at initial CABG and in 5% (1 of 20) who had repeat CABG. These operative mortality and morbidity risks are lower than those reported for similar patients who undergo PTCA.