Body surface potential mapping is superior to 12-lead electrocardiogram in detection of acute and old myocardial infarctions. We examined the capability of the ST-T integral and T wave to detect exercise-induced ischemia in body surface potential mapping. Body surface potential mapping with 123 channels was recorded in 70 subjects: 45 coronary artery disease (CAD) patients and 25 healthy controls during supine bicycle exercise testing. Of the patients, 18 had anterior, 14 posterior, and 13 inferior ischemia documented by coronary angiography and thallium scintigraphy. The ST-T isointegral area, as well as the positive and negative ST-T area, and the T-wave apex amplitude were determined. Discriminant index analysis was used to find the sites that optimally separated patient subgroups from other patients and controls. In the pooled CAD group, the optimal sites for detecting the decrease in ST-T isointegral, in the positive ST-T area and in the T-wave amplitude were over the left side (ST-T isointegral area: CAD -3.8 +/- 14 microVs and controls 24 +/- 14 microVs; T-wave amplitude: CAD 3 +/- 110 microV and controls 190 +/- 90 microV; P <.001, both). The area under the receiver operating characteristic curve for the decrease in ST-T isointegral, in the positive ST-T area, and in the T-wave amplitude and for the ST depression were 94%, 95%, 92%, and 93%, respectively. T wave performed especially well in patients with multivessel disease. In stepwise logistic regression analysis, using the presence of CAD as the dependent parameter, the decrease in the positive ST-T area and ST depression were the only parameters that entered the model. ST-T area and T-wave amplitude are sensitive and specific markers of transient myocardial ischemia. ST-T area contains information additional to ST depression and has thus independent discriminative value in ischemia detection.