Ninety-five HIV-infected children aged 3-5 and 6-14 years were examined. Clinical picture matched primary symptoms of stage IIV (phase of generalized lymphadenopathy by Pokrovsky V.I. classification, 1989) and included basic symptoms associated with HIV cytopathogenic action. Local opportunistic infections, either without damage of vital organs (phase IIIA of the secondary stage), or with damage of these organs (phase IIIB) were observed in patients with pre-AIDS. Generalized opportunistic infections and malignant tumors developed in patients with AIDS (phase IIIB and terminal stage IV). High frequency of bacterial infections, bacterial sepsis, splenomegaly, respiratory, gastrointestinal, cerebral, cardiac, common-infections syndromes, and rapid progression characterized the disease in young children. Local and generalized viral, fungal and protozoal infections were more frequently revealed in older children. Immunological alterations (T cell immunodeficiency, polyclonal activation of B lymphocytes, abnormalities of neutrophil metabolism) were diognosed in all children with phase IIV and were the most pronounced in young children. Progressive B lymphocyte polyclonal activation in young children, T cell immunodeficiency in older children and activation of neutrophil metabolism in those with pre-AIDS were observed. T cell immunodeficiency, B lymphocyte polyclonal activation, decreased neutrophil metabolism progressed steadily in all the patients with AIDS.