We have investigated the role of platelet-derived growth factor (PDGF) for the growth of cultured Kaposi's sarcoma (KS)-derived cells. They were found to bind 125I-PDGF-AA and 125I-PDGF-BB in a manner which is consistent with the presence of both PDGF A-type and PDGF B-type receptors. Furthermore, KS cells responded mitogenically to both PDGF homodimers. This shows that KS cells have functional A- and B-type PDGF receptors, suggesting an important role of PDGF for the growth of KS cells in vitro. In addition we found that KS cells produce PDGF-A chain mRNA in response to PDGF stimulation. This suggests that a PDGF-induced autocrine stimulation involving PDGF-AA which could amplify the response to PDGF occurs in these cells.