The objective of this study was to determine if human prostate carcinoma-associated tumor markers were expressed by Dunning rat prostate carcinomas. Frozen and formalin-fixed paraffin-embedded tissues from 12 different sublines of Dunning tumors were evaluated for marker expression by immunoperoxidase staining by using a panel of 9 monoclonal antibodies, including antibodies against human PAP and PSA. None of the Dunning tumors were found to express any of the human prostate tumor markers. Both fixed and live immunofluorescent assays were performed on 5 cultured Dunning tumor cell lines, evaluated either as single cells or as monolayers. As with the Dunning tumor tissues, none of the cell cultures expressed any of the 9 human prostate tumor markers. The lack of antigen expression by the Dunning tumor tissues and cell lines suggests that these human prostate tumor markers are quite species specific. These results limit the use of the Dunning prostate tumors as models to explore the preclinical application of these human prostate carcinoma-associated monoclonal antibodies and their target antigens.