In human malignant mesothelioma cell lines an elevation of the expression of the genes for the PDGF A-chain, PDGF B-chain, and PDGF beta-receptor was found compared to normal mesothelial cells. As ovarian epithelial tumors originate from the ovarian surface epithelium, which is of mesothelial origin, we investigated PDGF chain and PDGF receptor mRNA expression in six human ovarian cell lines of epithelial origin and a granulosa tumor cell line. All six investigated ovarian epithelial tumor cell lines expressed the PDGF A- and B-chain genes, while the granulosa tumor cell line expressed the PDGF A-chain gene only. Expression of PDGF receptors was not found in the epithelial or granulosa tumor cell lines. Cytogenetic and molecular biological studies did not provide evidence for rearrangement or genomic amplification of the PDGF B-chain. Expression of PDGF was also demonstrated in ovarian tumors in vivo. Frozen sections of six serous ovarian carcinomas stained positive with an antibody against PDGF and negative with antibodies against the PDGF alpha- and beta-receptors. These results suggest that PDGF expression might be a useful marker for ovarian carcinomas.