HIV infection is associated with abnormalities of cytokine production. A number of cytokines (IL-1, IL-6, TNF-alpha, interferons-alpha and -gamma) are produced at an increased level in vivo, whereas the production of IL-2 is decreased. This latter abnormality certainly plays an important role in the immunodeficiency of AIDS patients. Monokines (IL-1, IL-6, TNF-alpha) stimulate HIV replication in vitro, whereas the interferons decrease it. Cytokine effects on the in vivo spreading of HIV remain however to be determined. Cytokines may also be mediators of the clinical manifestations of AIDS. IL-1, IL-6 and TNF-alpha may induce tissue lesions of opportunistic infections and HIV encephalopathy. Cytokines, and mainly IL-6, may stimulate the growth of malignant cells in Kaposi sarcomas and in lymphomas. A better knowledge of the roles of cytokines in HIV infection may allow new therapeutic approaches using either recombinant cytokines or specific antagonists, with the aim of inhibiting both HIV spreading and the clinical manifestations of the infection.