The aim of this study was to clarify the effect of preinfarction angina on heart rate variability (HRV) in anterior wall acute myocardial infarction (AMI). A total of 36 patients experiencing their first anterior wall AMI were prospectively examined. The patients were divided into 2 groups according to the presence (group A, n=24) or absence (group B, n = 12) of preinfarction angina. HRV was assessed on 24-h Holter electrocardiograms recorded on day 3. Peak creatine kinase activity was significantly lower in group A than in group B (2,747+/-1,939 vs 4,891+/-2,639 IU/L, p<0.05). The SD of all RR intervals and ultra-low frequency, very low frequency, and low frequency powers was significantly less reduced in group A than in group B (86+/-24 vs 64+/-22 ms, p<0.05; 2,098+/-1,462 vs 867+/-502 ms2, p<0.01; 1,430+/-1,042 vs 546+/-344ms2, p<0.01; and 354+/-272 vs 186+/-136ms2, p<0.05; respectively). High frequency power, low frequency/high frequency, and pNN50 did not differ significantly between the 2 groups. In conclusion, preinfarction angina has a favorable influence on HRV in the early phase of anterior wall AMI.