Gilbert's syndrome (idiopathic unconjugated hyperbilirubinemia) is a benign hyperbilirubinemia found in the general population. We report one case in which the exacerbation and remission of hyperbilirubinemia closely correlated with the psychosis of schizophrenia. Some studies have reported that schizophrenic individuals had a significantly higher frequency of hyperbilirubinemia than patients suffering from other psychiatric disorders and the general healthy population. Stress and fasting are well-known contributors to elevated plasma bilirubin levels in patients with Gilbert's syndrome. A 38 year old woman inpatient with acute schizophrenic symptoms had a bilirubin plasma level of 2.7 mg/dl. She was treated with risperidone that produced no adverse effects on hepatic function. Schizophrenic symptoms improved and a decrease in bilirubin plasma concentration was observed.