Earlier we found that the transforming activity of growth factors in blood serum of AIDS and Kaposi's sarcoma patients was considerably higher than that in healthy donors' blood serum. This activity was estimated by studying the ability of serum to induce anchorage-independent growth of NIH-3T3 mouse fibroblasts in the semisolid culture medium supplemented with 0.33 % agar. Here we showed that the treatment of Kaposi's sarcoma patients with laferon (recombinant α2b-interferon) caused a significant decrease in the level of transforming activity in blood serum of all treated patients and this decrease positively correlated with a substantial improvement of their health state. Two cellular models were used for the study of the role of transforming growth factors in the modulation of cytopathogenic effects of HIV-1 infection - MT-4 line of T-lymplwblastoid cells infected with BRU strain of HIV-l (model of acute lytical infection) and the same cells infected with IIIB virus strain (model of chronic infection). Cytopathogenic virus effects were estimated by counting the part of dead cells and the number of giant cells. The amount of p24 virus protein was also determined. It was found that transforming growth factor beta and I or epidermal growth factor (transforming growth factor alpha analogue) increased the negative HIV-l effects in the experimental model of acute infection. The action of these cytokines was not so uniform in the case when the cellular model of chronic infection was use in the study. Thus, HIV-I infection is accompanied by the increased transforming activity of growth factors in blood serum of AIDS and Kaposi's sarcoma patients and these growth factors could be responsible for cytopathogenic effects observed in AIDS patients. This could partially explain why the successful treatment of Kaposi's sarcoma patients with α2b-interferon is accompanied by an decrease of the transforming growth factors activity in blood serum of the treated patients.