The results of examination of 87 children who died from a generalized cytomegalovirus infection in Elista (66 cases) in 1984-1985, 1988-89, and in Leningrad (21 cases) in 1988-89 are available. In the Elista material a considerable increase (from 21 to 66%) of severe forms of accidental transformation of thymus is observed in the second period comparing to the first one. The causes of a serious worsening of the immunological background remain unclear. Cytomegaly represented 3.85% of all dead children in the pathology department of the First Children Hospital of Leningrad. There was sialadenitis in 4 cases and generalized infection with involvement of the lungs, liver, kidneys, brain, myocardium, pancreas, adrenals in 17 cases. Cytomegaly was diagnosed in 3 of 5 cases of primary immunodeficiency. Diagnosis in some cases was confirmed by the DNA cytomegalovirus detection by means of PCR reaction.