Autoimmune hepatitis (AIH) is the chronic inflammatory liver disease of unknown etiology, demonstrating progressive injury of liver, finally leading to insufficiency of this organ. Possible association between clinical forms, course and prognosis of AIH has been considered recently. Aim of this study is to evaluate autoimmune hepatitis exacerbation risk in respect to epidemiological, clinical and laboratory signs demonstrated in patients with freshly diagnosed AIH. Retrospective study included 42 patients hospitalized in Liver Unit of Department of Infectious Diseases Medical University of Bialystok between 1999 and 2003, suspected for autoimmune hepatitis. In majority of patients onset of the disease was sudden and associated with significant increase of ALT activity. The most frequent, first sign of the disease was jaundice, that was observed in over 50% among patients, pruritus was reported by 1/4 patients. In 12 patients (41.4%) beginning of the disease was oligosymptomatic, i.e. without jaundice and pruritus. These patients demonstrated significantly lower ALT activity, bilirubin and gamma-globulin concentrations. Moreover prevalence of antinuclear antibodies in this group was less frequent, and frequency of hospitalization because of AIH exacerbations was also lower. Concluding, oligosynptomatic course of the disease accompanied by lower ALT activity can be related to better prognosis of AIH, and indicate mild course associated with low risk of exacerbations. On the c:her hand faster progression of the disease can be expected in younger patients demonstrating significant increase of ALT activity at the moment of initial diagnosis.