The purpose of the study was to examine the differences between first and second myocardial infarctions with respect to improvement in measures of heart rate variability (HRV). The study population comprised 48 non-diabetic patients with acute myocardial infarction (AMI), and with angiographically documented coronary artery occlusion and successful reperfusion. The subjects were grouped as 35 cases with a first AMI attack and 13 with their second AMI. Two weeks after the onset of infarction, indices of HRV were higher in first infarction cases than in second infarction cases. In the latter, there were no significant increases in HRV indices from day of onset to 2 weeks later, nor were there any significant changes in left ventricular ejection fraction (LVEF) from onset to 3 weeks later. All patients studied had a patent infarct-related artery 3 weeks later. We found sustained low values of HRV after a second AMI. Different risk stratification may be needed between uncomplicated first AMI and second AMI cases.