Gilbert's syndrome is defined as a hereditary, mild, chronic, unconjugated hyperbilirubinemia occurring in the absence of overt hemolysis or any other evidence of liver disease. It is caused by a mutation of the specific UDP glucuronosyl transferase conjugating bilirubin with glucuronic acid resulting in a reduced activity of this enzyme. Gilbert's syndrome is considered as a rather benign disorder without necessity of any therapeutic intervention. It is therefore crucial to establish a correct diagnosis and differentiate this syndrome from serious disorders of the liver tissue. In recent years strong antioxidant effects of bilirubin were demonstrated in numerous studies and the protective role of hyperbilirubinemia in the pathogenesis of various oxidative stress-mediated diseases was suggested. Gilbert's syndrome and its relationship to associated disorders such as hemolysis, pigment cholelithiasis, neonatal jaundice, schizophrenia and drug interactions are also being discussed.