The effectiveness of vaccination against virus hepatitis B (VHB) in the arid region of the Aral, endemic with respect to VHB, was evaluated. The character of specific immune response in 101 immunized children and in 12 adults belonging to a high risk group with respect to VHB. The vaccination of children was shown to be highly effective (96%). The average concentration of anti-HBs antibodies in these children was 856--133 IU/L after completed vaccination and 733--238 IU/L after revaccination. The comparative analysis of antibody levels in children at different periods after complete vaccination indicated that the level of anti-HBs antibodies in recipients decreased with the increase of time elapsed after the moment of vaccination. The effectiveness of the immunization of adults was low, which was probably due to the specific features of immune response to vaccination characteristic of their age and, in one case (a female recipient), to the presence of HBsAg.