We evaluated a 3-year clinical follow-up in 53 patients with unsuccessful PTCA, due to failure to reach the lesion (control-group) in comparison to a "matched pairs" group of 53 patients, in whom PTCA had been performed (PTCA-group). There were no deaths in the PTCA-group compared to 3 deaths (5.7%) in the control-group (ns). Two patients (3.8%) and three patients (5.7%), respectively, suffered an acute transmural myocardial infarction during the follow-up period (ns). Coronary artery bypass grafting (CABG) had been performed in five patients (9.4%) following PTCA, and in 17 patients (32.1%) of the control-group (p less than 0.002). The overall rate of serious cardiac events (death, myocardial infarction or CABG) amounted to 13.2% (seven patients) in the PTCA-group and to 43.4% (23 patients) in the control-group (p less than 0.002). Only in the PTCA-group was a repeat PTCA performed in 15 patients (28.3%) with restenosis (p less than 0.00003). 35 of 53 patients in the PTCA-group (66%) and 27 of 50 survivors in the control-group were free of symptoms at the end of follow-up (ns). These results demonstrate that PTCA in patients with single-vessel disease is followed by a marked reduction of serious cardiac events, predominantly of bypass-operations, but the necessity of a second PTCA-procedure in case of restenosis has to be considered.