Electrocardiographic R-R interval variations were assessed to determine the functional integrity of the cardiac vagal nervous system in 20 normal controls and 71 cirrhotic patients. The ratio of the coefficient of variation to standard prediction value was used as an index. The cirrhotic patients showed significant reductions in the ratio of the coefficient compared with controls (0.71 +/- 0.27 vs 0.91 +/- 0.14; P < 0.01). There was a significant relationship between decreased R-R interval variation and the liver function tests. The ratio of the coefficient increased with improvement in encephalopathy, and decreased with the development of encephalopathy. These results show that there is dysfunction of the cardiac vagal nervous system in patients with liver cirrhosis, and that this abnormality is partially reversible and might be related to liver dysfunction.