BACKGROUND: Autonomic dysfunction is common in patients with chronic liver disease, but it is still unclear whether acute hepatitis coincides with alterations in autonomic functions. METHODS: We evaluated the heart rate variability (HRV) of 10 patients with acute hepatitis (6 males, 4 females; mean age, 44.0 y; range, 20-69 y). Frequency-domain analysis of short-term and stationary R-R intervals was performed on the first day of admission to detect low-frequency power (LF; 0.04-0.15 Hz), high-frequency power (HF, 0.15-0.40 Hz), the ratio of LF to HF (LF/HF), and LF in normalized units (LF%). The same measurement was repeated on the 7th day of admission. RESULTS: We found that there was a significant increase of HF as well as variance of the R-R interval on the 7th day after admission (P < 0.05). There was a significant negative correlation between HF and the change of total bilirubin (P < 0.05). CONCLUSIONS: The study demonstrates a change in cardiac vagal tone associated with acute hepatitis by analysis of HRV, and such alteration is less pronounced later during the clinical course of acute hepatitis.