The relationships among moderate alcohol use, autonomic tone, and arrhythmogenesis in older adults have not been adequately studied. Knowledge about these relationships is of increasing importance in light of population aging and recent epidemiological findings that associate moderate alcohol use with decreased rates of coronary artery disease. The purpose of this study was to assess the association between moderate drinking and autonomic tone in older women. Fifty-two Caucasian female participants (age 69 +/- 5.2) were enrolled in the study. Autonomic tone was estimated by time-domain and frequency-domain measures of heart rate variability. Multivariate analysis revealed that alcohol consumption rate in the sample accounted for approximately one third of the 24-h variability in the SDNN and the SDANN, measures of variability cycle lengths of 24-h and more than 5-min, respectively. Significant contributions of alcohol consumption rate to the shorter-term time-domain measures rMSSD and ASDNN, all frequency-domain measures, and HR were not confirmed. However, repeated measures ANOVA revealed that, between the hours of 0000 and 0600, women who drank approximately 0.5 to 3 standard drinks per day had significantly lower [log] HF and [log] LF power compared to abstainers and a tendency toward sympathetic predominance during the evening and nighttime hours. The authors discuss the implications of these findings.