OBJECTIVE: To evaluate autonomic nervous tone during general and epidural anesthesia. METHODS: Thirty-two female patients(ASA grade I-II), scheduled for elective hysterectomy, were randomized to receive epidural anesthesia (group EA, n = 16) or general anesthesia (group GA, n = 16). The changes of HRV were observed with power spectral analysis of heart rate variability (HRV-PSA) at the following time intervals: immediately pre-anesthesia (T1), 15 min after induction (T2), 1 min after incision (T3), dragging uterus (T4), after removing uterus (T5) and end of surgery (T6). RESULTS: Patients in group EA demonstrated a significant advance in LF/HF at T4 and descending in LF and HF at T5, T6 to compare with T1, LF, HF and LF/HF remained unchanged at the rest time intervals. In group GA, compared with T1, LF, HF and LF/HF dropped remarkably except for an increase in LF/HF at T6. CONCLUSION: The autonomic nervous tone is inhibited by both epidural and general anesthesia. EA reveals a shift in the sympathovagal balance toward sympathetic predominance. GA is associated with a shift toward parasympathetic predominance intraoperatively, while postoperatively appears a dramatic increase in LF/HF. Relative to EA, there is a greater effect on autonomic nervous system with GA.