The aim of this study was to determine the efficacy of transcutaneous electrical nerve stimulation (TENS) in the treatment of chronic stable severe angina pectoris. In a short-term study the effect of TENS was studied in 10 male patients with angina pectoris (functional class III and IV). All patients had previously been stabilized on long-term maximal oral treatment. The effects of the treatment were measured by means of repeated bicycle ergometer tests. All patients had an increased working capacity (16-85%), decreased ST segment depression and reduced recovery time during TENS. No adverse effects were observed. A long-term study of TENS on similarly selected patients showed beneficial effects in terms of pain reduction, reduced frequency of anginal attacks, increased physical activity and increased working capacity during bicycle ergometer tests. An invasive study was carried out with respect to systemic and coronary hemodynamics and myocardial metabolism during pacing provoked myocardial ischemia in 13 patients. The results showed that TENS led to an increased tolerance to pacing, improved lactate metabolism, less pronounced ST segment depression. A drop in systolic blood pressure during TENS treatment at identical pacing rates indicated a decreased afterload. An increased coronary flow to ischemic areas in the myocardium was supported by the fact that the rate pressure product during anginal pain increased during TENS.