BACKGROUND In an effort to discover new prostate-specific antigens (PSAs) to enhance our understanding of the functions and behavior of the prostate and the complex processes involved in prostate tumor progression, the structure and function of the PSM antigen has been elucidated. METHODS The PSM antigen was recognized using the 7E11-C5.3 monoclonal antibody, generated against the LNCaP human prostate adenocarcinoma cell line. The PSM cDNA was isolated by PCR, using tryptic peptides of immunoprecipitated PSM to design degenerate primers. RESULTS The prostate specific membrane antigen (PSM) is a 100 KD glycoprotein which appears to be a type II integral membrane protein. The protein and cDNA have been extensively characterized and the findings reviewed in the report. CONCLUSIONS PSM, a new prostate antigen is valuable as a marker for hematogenous micro-metastatic tumor dissemination as detected in RT-PCR assays of peripheral blood. PSM has many properties that may be potentially useful as a molecular target in monoclonal antibody directed strategies of tumor imaging and therapy.