Alterations in several neurotransmitter systems in brain have been implicated in the pathophysiology of hepatic coma (HC). Studies on human autopsy material are few. We investigated 3H-quinuclidinylbenzilate (QNB), 3H-spiperone, 3H-imipramine, 3H-PN-200-110, 3naloxone, 3H-flunitrazepam, 3H-muscimol, 35S-t-butylbicyclophosphothionate and 3H-cyclohexyladenosine binding sites in frontal cortex from seven patients with HC and five controls. The density of 3H-QNB binding sites was significantly decreased and the affinity slightly increased in HC. The functional significance of these selective changes in muscarinic receptor binding sites is unclear. Further studies evaluating cholinergic function in HC are indicated. Acute studies in animals point to an increase in GABA and BZ binding sites in HC. The present results show that the BZ/GABA-receptor-chloride-ionophore complex is unchanged in HC in man. Serotonergic (5HT-2), adenosine (A-1), imipramine (5HT uptake sites), opiate (naloxone) and calcium channel antagonist binding sites are unchanged in HC.