The impact of treatment on progression of fibrosis in autoimmune hepatitis (AIH) is unknown. We assessed the changes in liver fibrosis before and after treatment among these patients. Nineteen AIH patients who had paired liver biopsies were studied. Of these, seven had been treated with 6 months of cyclosporine A and the rest with 6 months of prednisolone for induction of remission. Thereafter all had been maintained on azathioprine. Biopsy specimens before and after treatment were reviewed by one pathologist and scored by the Ishak method. Mean fibrosis stages before and after treatment were compared. Also, factors predicting significant fibrosis (stage > or =3) and cirrhosis (stage > or =5) at presentation were assessed. Mean interval between biopsies was 3.38 years. Mean fibrosis stage decreased from 4.53 to 2.16 following treatment (P < 0.001). Mean decrement in inflammatory grade was 8 scores (range, 4-10) in patients in whom fibrosis improved, and 2 scores (range, 0-4) in patients in whom fibrosis did not decrease after treatment (P < 0.001). ALT-to-platelet ratio was the best predictor of significant fibrosis and also cirrhosis. Fibrosis commonly improves after immunosuppressive treatment in AIH. ALT-to-platelet ratio can predict accurately the presence of significant fibrosis and cirrhosis in AIH.