The production of cytokines by HIV-infected cells from adherent tissues as well as their effects on HIV replication in the same cells were investigated. CD4-transfected HeLa-T4-6c epithelial cells, CD4-positive normal lung fibroblasts and CD4-negative RD rhabdomyosarcoma cells were infected with HIV-1. All cultures were permissive for virus replication, which was completed within 48-72 h by Hela-T4-6c and RD cells and 2-3 weeks in normal fibroblasts. During the course of HIV replication, a series of cytokines (particularly IL-6 and TNF alpha) was produced and released in parallel to the peak of virus growth, in amounts varying with the cell system studied. Treatment of cultures with recombinant cytokines given at concentrations in the range of those induced by HIV-1 indicated that IL-6 and TNF alpha caused an increase of: i) CD4 expression, ii) HIV absorption to uninfected cells, and iii) release of infectious virions by infected cells. The fact that HIV-1 absorption and spread can be mediated by HIV-induced cytokines may be relevant in the pathogenesis of the in vivo disease, as it may constitute a possible self-enhancing model of HIV infection also in the solid tissues.