Tacrolimus (FK506) is being used as immunosuppressant in solid organ transplantation. However, its nephrotoxic and neurotoxic effects are well recognized. Recently reversible hypertrophic cardiomyopathy under tacrolimus has been described in five children.1 In order to evaluate myocardial toxicity of the drug, we examined the cardiac findings at autopsy in adults and children following primary liver transplantation (OLTx) under tacrolimus and compared them with autopsy findings of patients who died of end-stage liver disease without OLTx and tacrolimus.