An increase in the incidence of viral hepatitis was observed in the autumn of 1986 in one of the districts of southern Uzbekistan. The clinico-epidemiological data and highly sensitive tests for hepatitis A (HA) and B (HB) markers showed the absence of HB infection in most of the patients and prevalence of HA among children. In 68.7% of the patients, non-A-non-B hepatitis with fecal-oral mechanism of transmission of the infection was diagnosed. The bulk of HnAnB patients consisted of adults of 20-29 years. Pregnant women experience severe forms of the disease. Solid-phase enzyme-immunoassays and immune electron microscopy revealed in one fecal specimen from patients the antigen of non-A-non-B hepatitis serologically identical to that causing a rise in the incidence in northern Turkmenia in 1984-1985.