HIV-1 transcripts have been detected in AIDS-related Kaposi's sarcoma (KS) tissues within the factor XIIIa + dermal dendrocytes present in the tumor. Various cytokines and growth factors have been shown to influence the growth of KS-derived cells in vitro. HIV-1 preferentially infects CD4+ cells and has also been found to infect some CD4- cells in vitro. The susceptibility of cultured KS cells in vitro to infection with HIV-1 and the expression of interleukin (IL)-1 beta, IL-6 and basic fibroblast growth factor (bFGF) after exposure to HIV-1 was examined. The susceptibility of two different KS-derived cell cultures to HIV-1 infection was examined by the expression of p24 antigen, detection of proviral sequence and electron microscopy. The expression of IL-1 beta, IL-6 and bFGF was detected by enzyme-linked immunosorbent assay and reverse transcriptase polymerase chain reaction. KS-derived cells can be infected by HIV-1 in vitro. Both KS-derived cells were found to express CD4 mRNA. The expression of IL-1 beta and IL-6 was increased, whereas the expression of bFGF was not stimulated after exposure of KS cells to HIV-1. These experiments describe the in vitro infection of KS-derived cells by HIV-1 and the expression of various cytokines and growth factor following infection. The increased production of cytokines observed following such infection may be involved in the pathogenesis of AIDS-related KS.