In a consecutive series of 400 patients treated by percutaneous transluminal coronary angioplasty 212 had single vessel disease, 142 had multivessel disease with only one vessel dilated, and 46 had multivessel dilatation. In addition sequential stenoses were dilated in the same vessel in all groups. There was no mortality among patients with single vessel disease. Success rates varied from 83% to 90% according to the artery in which angioplasty was attempted. Urgent surgery was required by 3.8%. Primary success was lower (74%) in the presence of multivessel disease and complications were more frequent, with four deaths (2.8%). In 46 patients with multivessel disease in whom all important lesions were dilated during the same procedure the overall primary success rate was 76% and within the last year of the study it was 91%. One (2%) patient died and three (7%) required urgent surgery. Twelve (86%) out of 14 stenosed vein grafts were successfully dilated and eight (53%) chronically occluded vessels were re-opened; in both groups there were no deaths, no infarctions, and no need for urgent surgery. In all groups symptoms improved greatly and predischarge exercise tests showed that there was no reversible ischaemia in 94% of patients with single vessel disease or in 65% of patients with incomplete revascularisation. Six months after the procedure 95% of the patients had improved symptomatically and 80% had normal exercise tests after one year. Percutaneous transluminal coronary angioplasty is the method of choice in single vessel disease and its use also results in a high proportion of other patients becoming symptom free. Complication rates are low and for selected patients results that are equivalent to those of cardiac surgery are obtained.