BACKGROUND Although prostate-specific antigen (PSA) has aided significantly in the diagnosis of prostate cancer, more sensitive and accurate assays are needed. Presently, we are developing a sensitive immunoassay for hK2 protein for the detection of prostate cancer. METHODS Polyclonal and monoclonal antibodies specific for hK2 were produced and used for Western blot analysis and immunohistochemistry for detection of hK2 protein in serum and human tissues. The reverse-transcriptase polymerase chain reaction (RT-PCR) was utilized to detect hK2 mRNA from patient blood samples. RESULTS Western blot analysis demonstrated that the antibodies used are monospecific for hK2. Immunohistochemistry showed that hK2 is expressed only in prostatic epithelia. An RT-PCR study showed that hK2 mRNA would be a useful candidate for early detection of prostatic micrometastasis. CONCLUSIONS Monospecific antibodies for hK2 have been developed for detecting hK2 protein. Our studies indicate that hK2 may be a useful marker for prostate cancer.