This study evaluated the prognostic significance of continuous on-line vectorcardiography (VCG) during elective coronary angioplasty (percutaneous transluminal coronary angioplasty, PTCA). Patients (n = 192, mean age 58 ± 10), treated with elective and initially successful PTCA, were included. VCG monitoring was started before start of the PTCA procedure and was carried out during the entire procedure. ST vector magnitude (ST-VM) was monitored. A 6-month follow-up was obtained. Main outcome measures were the frequency of cardiac events and revascularization during follow-up. During follow-up, 1 patient died, 6 suffered a nonfatal myocardial infarction and 50 were revascularized. Angiography revealed restenosis in 88% of the patients who had a revascularization. In the total patient group, the VCG predictor of revascularization was the total ischemic time of all ST-VM episodes (p = 0.05). Clinical predictors of revascularization were diabetes mellitus (p < 0.01), a more severe type of lesion (type B; p < 0.01), percent post-PTCA stenosis (p < 0.05), nominal balloon size (p < 0.01), maximum balloon pressure (p < 0.05) and no stent implanted (p < 0.001). In a multivariate analysis all the above significant univariate variables of revascularization were entered. Total ischemic time of ST-VM (p < 0.01) was the best variable giving independent prognostic information. In the nonstent group, total ischemic time of ST-VM (p < 0.01) was the only independent predictor of a further revascularization. In conclusion, VCG monitoring during elective PTCA gives on-line information that identifies patients at an increased risk of a revascularization during 6 months after the initial procedure.