The value of exercise ECG (ExT) in predicting the occurrence of restenosis after successful single-vessel percutaneous transluminal coronary angioplasty (PTCA) was assessed in 94 patients (pts). There were 83 pts with complete and 11 with incomplete revascularisation. In all cases ExT were made prior to the procedure, immediately after, 3 and 6 months after PTCA. In group of 48 pts without restenosis an abnormal ExT was present in 19 (39.6%) pts immediately after PTCA and in 13 (27.1%) pts in 6 month of observation. Among 46 pts with restenosis an abnormal ExT was observed in 27 (58.7%) pts immediately after PTCA and in 42 (91.3%) pts in time of 6 months control. Four (8.7%) pts showed negative ExT despite of restenosis. After 3 months of observation multivariate analysis of 11 factors revealed 2 factors related to restenosis: ST segment depression and chest pain during ExT. The positive predictive value for restenosis was 60.5% for those factors. After 6 months of observation multivariate analysis revealed 3 factors related to restenosis: ST segment depression, double product and maximal blood pressure during ExT. The positive predictive value for restenosis was 64.7% for those factors. It is concluded that our diagnostic strategy provides a useful clinical tool for detecting patients with high risk of restenosis who may require repeated coronary angiography.