In this paper we characterize hPARM-1, the human ortholog of rat PARM-1 (prostatic androgen-repressed message-1) and demonstrate its role in prostate cancer. Immunofluorescence microscopy and ultrastructural analysis revealed the localization of hPARM-1 to Golgi, plasma membrane and the early endocytic pathway but not in lysosomes. Biochemical and deglycosylation studies showed hPARM-1 as a highly glycosylated, mucin-like type I transmembrane protein. Analysis of expression of hPARM-1 in various human tissues revealed its presence in most human tissues with especially high expression in heart, kidney and placenta. Androgen controls the expression of the gene as a marked 7-fold increase is seen in the androgen-dependent prostate cancer cell line, LNCaP on androgen stimulation. This is further supported by its decrease in expression in CWR22 xenograft upon castration. Moreover, ectopic expression of hPARM-1 in PC3 prostate cancer cells increased colony formation, suggesting a probable role in cell proliferation. These results suggest that hPARM-1 may have a role in normal biology of the prostate cell and in prostate cancer. © 2007 Wiley-Liss, Inc.