Neurotoxicity represents a serious complication following orthotopic liver transplantation. Neurotoxicity may be evoked by various perioperative factors or develop due to drug-specific toxicity of immunosuppression. We evaluated the incidence of neurotoxicity in 121 patients, 61 randomly assigned to FK506 and 60 to CsA-based immunosuppression. The incidence of moderate or severe neurotoxicity was markedly higher in patients treated with FK506 in the early postoperative period (21.3% vs. 11.7% in patients receiving CsA), after retransplantation (100% vs. 0% in patients receiving CsA), and late (8 of 10 patients; P < or = 0.05 vs. CsA). Furthermore late neurotoxicity was highly associated with severe infections and MOFS, which had a lethal outcome in more than 50% of the patients. Patients who subsequently died developed neurologic symptoms in 67% of the cases. These patients also experienced moderate or severe neurotoxicity significantly more often in the early postoperative period compared with patients with a successful outcome (50% vs. 17.3%; P < or = 0.01). However, various blood and serum parameters, including ALT, bilirubin, urea, creatinine and glucose, when analyzed alone or in multivariate fashion, also correlated significantly with the incidence and severity of early postoperative neurotoxicity, indicating that neurotoxicity following LTX may be caused by various factors and is not exclusively a drug-specific side effect of immunosuppression.