Autoimmune thyroid diseases, including Hashimoto`s thyroiditis (HT), are common organ-specific autoimmune disorders that often occur in conjunction with other autoimmune diseases. Autoimmune hepatitis (AIH) is a relatively rare disease of unknown etiology. In this condition, progressive destruction of the liver parenchyma occurs. Without proper treatment with immunosuppressive agents, such as prednisone and azathioprine, this condition leads to cirrhosis and liver failure. Timely detection and appropriate treatment of the AIH is prerequisite for the long-term survival of affected patients. We report here a case of HT accompanied by AIH confirmed by liver biopsy. On the basis of this case report, we suggest that, a sustained elevation of aminotransferases refractory to thyroid dysfunction correction should result in a liver biopsy to differentiate AIH from other forms of liver dysfunction or secondary to thyroid disorders. Treatment should commence promptly. (J Korean Endocr Soc 24:287~292, 2009)