Hepatic innervation participates in the control of sinusoidal blood flow and in the regulation of certain metabolic functions of the liver. The study of the distribution of hepatic nerves has been hampered by the lack of adequate markers. We therefore tested the value of the neural cell-adhesion molecule (NCAM) as a probe for the study of parenchymal nerves in the normal and cirrhotic human liver. Four antibodies against various epitopes of NCAM were tested by light and electron microscopic immunohistochemistry: Leu19, ERIC-1, VC1.1, and HNK-1. Their reactivity was compared with that of antibodies against the following neural cell markers: S100 protein, neurofilaments, and neuron-specific enolase (NSE). The tissue reactivity of anti-NCAM antibodies was variable, suggesting a microheterogeneity of the NCAM molecule in the normal liver. Clones Leu19 and ERIC-1 proved to be the most sensitive of the anti-NCAM antibodies. Their sensitivity was superior to that of the antibodies directed against the other neural cell markers tested. In the normal liver, both Leu19 and ERIC-1 demonstrated a heterogeneous distribution of nerve fibers inside the hepatic lobule. Intralobular nerve fibers predominated in Zone 1. This might contribute to the constitution of distinct zonal microenvironments inside the hepatic lobule. In cirrhosis, no nerve fiber was detected inside parenchymal nodules; no nerve plexus was visible at the contact of proliferating neoductules. These alterations might contribute to the pathogenesis of the hemodynamic and metabolic disorders observed in cirrhosis.