This is a multicentre, multinational clinical study. It comprised two consecutive segments (A and B). Segment A was designed as a randomized, double-blind, double-dummy, active-controlled, two-arm parallel-group study. The patients received either budesonide or prednisone for 6 months. During segment B all patients received budesonide as an open treatment for additional 6 months.

In this confirmatory study the proportion of patients with complete response was compared between the two treatment groups. Complete response was defined as biochemical remission (=serum levels of ASAT and ALAT within normal ranges) at the individual last visit of segment A and lack of steroid specific side effects throughout segment A.

Inclusion Criteria:

• age 10 to 70 years
• Diagnosis of acute AIH according to Alvarez score
• normal range of TPMT activity
• normal ACTH test
• negative pregnancy test at screening for females of childbearing potential
• written informed consent

Exclusion Criteria:

• presence of Hepatitis A, B, C, E or G virus infection
• liver cirrhosis or clinical signs of portal hypertension
• PBC
• PSC
• history of hypersensitivity to the study medication