The relationship between ST reelevation at reperfusion and the occurrence of late potentials (LPS) in 35 patients with a first anterior infarction who had single vessel disease was investigated. All patients underwent a successful primary angioplasty and had a patent infarct related artery confirmed angiographically 4 weeks later. Patients were classified into groups based on changes in the ST level at reperfusion: patients with ST reelevation (group A, n = 22) and patients without ST reelevation (group B, n = 13). Signal-averaged ECG was performed 4 weeks after primary angioplasty to detect LPS. Cineventriculography was performed to measure left ventricular ejection fraction (LVEF) and evaluate regional wall motion of the infarct area (SD/chords). LPS were present in eight of the 22 group A patients (36%) and in none of the 13 group B patients (P < 0.05). Left ventricular function was impaired in patients in group A compared with patients in group B (LVEF: 5 1 +/- 12 vs 63 +/- 10, P < 0.01; SD/chords: -2.7 +/- 0.9 vs -1.9 +/- 1.1, P < 0.05). These data suggest that ST reelevation and myocardial damage at reperfusion are associated with the occurrence of LPS in patients with successfully recanalized infarct related arteries after acute anterior infarction.