Highly sensitive up-to-date research methods (enzyme immunoassay) for HbsAg and antibodies against HBsAg and HBcAg were employed to examine 565 adults and children living in the Kalmuck++ ASSR (Elista and adjacent regions), where in 1988-1989 cases of HIV-infection were recorded. Markers of HBV-infection were detected with a high enough frequency in the control group of children (15.2%). The prevalence of the infection in the adult population was at an intermediate level (38.9%). The high infectivity with HBV-infection was recorded among children who had been hospitalized before (for different diseases including chronic ones), among women who had undergone laboratory studies because of the diagnosis of HIV-infection in their children; among adult patients suffering from tuberculosis of morons from a closed boarding school. The highest frequency of HBV-infection marker demonstration was found in HIV-infected children (70%). The data obtained point to the necessity of vaccination against viral hepatitis B in risk groups (children and adults) and in the newborn as well as of raising the efficacy of preventing measures against infections transmitted via blood.