In the first series of 50 patients in whom percutaneous transluminal coronary angioplasty (PTCA) was attempted, the procedure was successful in 32. 23/32 patients were followed up clinically over 62.2 +/- 5.6 (SD) months. Repeated non-invasive laboratory tests were carried out in 15/23 patients. Moreover, 11/15 patients were restudied by arteriography at the end of the follow-up period. Early recurrence of the stenosis occurred in 5/32 patients (16%) and was again successfully treated by a second PTCA in 2. 3 patients underwent surgery as requested. 22/23 (95%) remained symptom-free during the follow-up period. The results of the non-invasive laboratory tests were in close agreement with the clinical findings. Coronary arteriography performed at the end of the follow-up period revealed an excellent lasting effect of PTCA in 8/11 patients. 2 showed a slight progression of the three stenoses treated by PTCA, and in 1 patient late recurrence of the stenosis was suspected since he had been symptom-free up to 2 weeks prior to restudy. Thus, in patients who are suitable for PTCA, this treatment is of long-lasting effect and represents an excellent alternative to coronary artery bypass surgery.