To assess the presence of residual myocardial ischemia, right atrial pacing was performed in 30 patients with 31 episodes of acute myocardial infarction (AMI) on the day before their discharge from the hospital. Ten patients had anterior, 11 inferior, and 10 subendocardial AMI. The atrial pacing was performed in the intensive care unit. The electrode was introduced by direct puncture of the antecubital vein and positioned under intracavitary ECG control. No complications occurred in any of the patients. Ischemic ST depression was observed in 14 patients. Only 1 of 10 with anterior AMI had a positive test, compared with 7 of 11 with inferior AMI and 6 of 10 with subendocardial AMI. It is concluded that right atrial pacing can be performed safely in patients soon after AMI, and that the procedure is sensitive in detecting residual myocardial ischemia. It is expected that this method will provide a tool for identifying high-risk patients, thus enabling better treatment and possibly a reduction in the rates of reinfarction and sudden death.