The cornerstone of AIH treatment is prednisolone, which usually leads to excellent clinical response. Thiopurines (azathioprine (AZA) and 6-mercaptopurine (6-MP) are used as a first choice steroid sparing agent. Chronic auto-immune hepatitis requires lifelong maintenance therapy in the majority of patients. Besides minimizing the risk of disease relapse and or progression, long-term treatment goals in AIH are to minimize side effects of treatment such as bone loss, diabetes and obesity with prednisolone and marrow depression and hepatotoxicity with thiopurines. Optimal dosing of thiopurines has long been established for other indications, but for AIH patients the optimal dosing is unclear. European and American guidelines differ in the advised starting dose and their recommendations are based on case series and expert opinions. Dosing based on body weight as well as fixed starting doses are applied in general practice, based on the physicians experience. When in long term clinical remission on combination therapy, thiopurine monotherapy is a well-accepted goal to eliminate steroid related side effects. The optimal thiopurine dose to be able to successfully withdraw prednisolone is uncertain. In this study two different strategies to eliminate steroids are compared.