Hepatitis A viral infection usually lasts up to 12 weeks, but in 3-16% of patients relapses may occur and the course of the disease is protracted. The outcome of hepatitis A is always good, so that antiviral therapy is not necessary. However, from the aspect of patients with protracted course of the disease up to a year, it might be important to restore clinical recovery in a shorter period of time. Knowing about antiviral and immunomodulatory effects of endogenous interferon (virally activated) in treatment of protracted hepatitis A, we introduced interferon-alpha in the 12th week of the disease and followed-up its effects on the further course of the disease. The study comprised 80 patients with established diagnosis of acute protracted hepatitis A, excluding hepatitis B, Epstein-Barr, cytomegalovirus, adenovirus or toxic liver lesion. In 40 patients treated with interferon we followed up the activity of aminotransferases and persistence of IgM-anti-HAV in correlation with the same parameters in 40 patients treated symptomatically. The registered persistence of aminotransferases' pathological activity was 20:30 weeks (interferon: symptomatic therapy). In greater doses interferon affected the length of persistence IgM-anti-HAV, 20:34 weeks (interferon: symptomatic therapy).