To improve symptomatic status and avoid reoperation, 122 initial and 7 repeat percutaneous transluminal coronary angioplasty procedures were performed in 116 patients with disabling angina pectoris at a mean of 26.8 months (range 2 to 132) after coronary bypass surgery. Marked angiographic improvement (greater than 30% reduction in diameter stenosis) was obtained in 107 (88%) of the 122 initial procedures and in all 7 repetitions. Mean stenosis was reduced from 78 +/- 13% (mean +/- standard deviation) to 25 +/- 13% (p less than 0.0001) and mean pressure gradient from 49 +/- 15 to 11 +/- 8 mm Hg (p less than 0.0001). Complications were: emergency surgery (three patients), Q wave infarction (one patient), myocardial infarction by enzyme criteria only (four patients) and non-occluding coronary dissection (one patient). There were no neurologic or peripheral vascular complications and no early deaths. One late death occurred 14 months after an unsuccessful but uncomplicated angioplasty procedure. At a mean follow-up of 8.3 months, 88 patients (76%) were free of angina or in improved condition. In patients followed up for at least 6 months, evidence of restenosis occurred in 9 (53%) of 17 saphenous veins, 1 (50%) of 2 proximal graft anastomoses, 4 (18%) of 22 distal graft anastomoses and 5 (14%) of 37 native coronary arteries. When coronary anatomy is suitable, percutaneous transluminal angioplasty is an attractive alternative to reoperation in symptomatic patients with prior coronary bypass surgery.