The paper presents the results of investigations of hepatitis E (HE), which have been made at the Department of Viral Hepatitides, M. P. Chumakov Institute of Poliomyelitis and Viral Encephalitides, Russian Academy of Medical Sciences. M. S. Balayan's discovery of hepatitis E virus permitted etiological interpretation of the cases of so-called non-A, non-B hepatitis with its fecal and oral transmission. The detection of antibodies to HE virus among different groups of the population of Russia (i.e. a hepatitis E nonendemic region of the world) suggests that they are frequently detected in the absence of disease notification. The fact that viral HE RNA has been detected in the pigs and wild boars inhabiting in the country is evidence in favor of an assumption that the virus is spread among these animals. The hypothesis for HE as a zoonosis is discussed in the paper.