The short term effects of epidural spinal electrical stimulation were studied in 10 patients with angina pectoris of New York Heart Association functional class III or IV. The antianginal pharmacological treatment given at entry to the study was regarded as optimal and was not changed during the study. The effects of epidural spinal electrical stimulation were measured by repeated bicycle ergometer tests. Treatment with epidural spinal electrical stimulation increased the patients' working capacity, decreased ST segment depression, increased time to angina, and reduced the recovery time. The observed effects did not seem to be correlated with any changes in myocardial oxygen demand during epidural spinal electrical stimulation and were additional to the benefits of the pharmacological treatment.