Heart rate variability (HRV) has recently been used to detect autonomic nerve tone, which is affected by various stresses. To test out hypothesis that HRV can determine surgical stress, we examined perioperative HRV in 30 patients with surgical treatment. Relations between HRV and factors of surgical stresses, such as duration of the operation, amount of blood loss at the operation, and developments of complications, were evaluated. Mean heart rate (HR) increased and other HRV indices decreased postoperatively. Most indices correlated significantly to the duration of the operation and amount of blood loss at the operation on postoperative day 1. Only the standard deviation of normal to normal RR intervals (SDNN) and HRV triangular index showed significantly low values in complicated patients. HRV measurement in the perioperative period showed a significant relation to surgical stress. The present results indicated that HRV may provide useful information with respect to surgical stress.