6 cases of HIV infection were revealed by enzyme immunoassay and immunoblotting among 144 children who had died in Elista. Another 5 children might have had HIV-infection but laboratory analyses either were lacking or gave doubtful results. Laboratory results were negative in 133 children. Similar severe changes of the lymphoid system typical for immunodeficiency were found in all children. These changes in HIV infection were characterized by lymphogenic generalized RNA infection. Complications (secondary diseases) in the form of DNA-virus infections (cytomegalia and herpes simplex), pneumocystosis and other viral and bacterial processes were observed in children of all groups. The disease was found mainly in Kalmyks. Blood examination of healthy Kalmyks revealed some differences in the form of significant decrease of the lysosomal cationic proteins content and the peroxydase activity of neutrophil leucocytes as compared to the same indexes obtained in Leningrad. There was also a tendency to the decrease of T-lymphocyte content. The children dying from immunodeficiencies lived mainly along the litoral of an ancient sea.