Abstract: Inborn errors of bile acid synthesis caused by enzyme defects are inherited metabolic rare diseases and mostly belong to the autosomal recessive hereditary diseases. They are clinically manifested as progressive cholestasis liver disease, neurological disorders, and fat-soluble vitamin malabsorption. The progressive cholestasis liver disease is characterized by conjugated hyperbilirubinaemia with raised transaminase, but normal γ-glutamyl transpeptidase (γ-GT), and a biopsy specimen shows giant cell hepatitis. The neurological disorders usually present with childhood-onset or adult-onset spastic paraplegia. Early diagnosis is important because oral administration of bile acids is effective for two disorders above. This article reviews pathophysology, clinical features and various enzyme defects of inborn errors of bile acid synthesis.