Among 71 patients, 19 (26.7%) experienced tacrolimus-related complications including 15 neurologic reactions and four problems with nephrotoxicity. Seven of these patients received grafts from cadaveric donors and 12 from living donors. Nine patients were children. The cohort included 5 female and 14 male subjects of mean age 26 +/- 20 (min 6, max 65) years. The common indications for the liver transplantation were cholestatic and metabolic diseases in pediatric patients, and viral hepatitis in adult patients. Blood tacrolimus levels were within the normal range. All patients with neurologic complications received antiepileptic therapy and drug conversion to rapamycin in 4 cases and to cyclosporine (CsA) in 11 cases. Six cases with Wilson disease and all cases with tyrosinemia experienced neurologic complications, which reversed in all but one case. In four cases with nephrotoxicity, we switched to rapamycin. Renal function improved in all cases. Patients with Wilson disease and tyrosinemia were more susceptible to the neurologic side effects of tacrolimus. In these cases we recommend the use of drugs with fewer neurologic side effects. Tacrolimus also has nephrotoxic effects, which can be reversed by converting to rapamycin.