The purpose of this study was to determine whether changes in the expression of platelet-derived growth factor (PDGF) and its receptors were associated with prostate cancer. Peroxidase-anti-peroxidase-immunoperoxidase labeling was used to detect the A and B chains and alpha and beta receptors of PDGF in 5 benign prostatic hyperplasias and 13 human prostate adenocarcinomas (Gleason grades 2 to 9). In all 5 benign prostatic hyperplasias, none of the PDGF antibodies (even at high titers, 1:50 dilutions) labeled the epithelial or the stromal cells. In adenocarcinomas, the A chain and alpha receptor antibodies labeled both epithelial and stromal cells. The intensity of the staining was relatively high in low Gleason grade (<6) and low in high Gleason grade (>7) tissue; however, the B chain and beta receptor antibodies failed to label either epithelial or stromal cells in any of the 13 adenocarcinomas. The data suggest that PDGF A and alpha receptor genes may be preferentially turned on in epithelial and stromal prostate tumor cells.