In this study, we investigated heart rate variability in women who exercise regularly, but with differing volumes of physical activity. Forty women participated and were allocated to either a "high" or "moderate" activity group. Heart rate as R-R intervals was recorded during supine rest and analysed using time domain, frequency domain, and Poincaré plot techniques. All time domain and Poincaré analysis measures revealed significant differences in heart rate variability between the "high" and "moderate" activity groups. Frequency domain analysis also revealed a significant difference between the two groups in absolute measures of high-frequency and low-frequency power, but not between measures such as the low-frequency/high-frequency ratio, proposed to represent the sympathetic/parasympathetic balance of cardiac control. The results demonstrate that there is a significant difference in heart rate variability between women who engage in "high" compared with "moderate" volumes of physical activity, which may have implications for cardiac autonomic health.