The production of alpha- and gamma-interferon (IFN) by peripheral blood cells in vitro and the concentration of serum IFN were studied in patients treated by hemodialysis at the Pelgulinna Tallinn Hospital and compared to controls. Out of 108 patients on hemodialysis, 19.4% were infected with hepatitis B (HBV), and antibodies to hepatitis C virus (HCV) were detected in 7.4%. During 3.5 years of observation, cases of hepatitis B and C infection among patients and medical staff were rare. The production of alpha- and gamma-IFN in 23 patients with HBV and/or HCV markers on hemodialysis and in 38 patients without markers was similarly decreased in comparison with the controls and the titers of serum IFN were similarly increased. Lack of reliable difference between IFN status of two groups of patients may be explained by the absence of clinical symptoms of hepatitis, confirmed by laboratory findings.