Gastrin-releasing peptide (GRP) belongs to the family of bombesin-like peptides. GRP was demonstrated to stimulate the proliferation and invasiveness of androgen-independent prostate carcinoma. GRP mediates its action through the membrane-bound receptor, GRP receptor (GRPR), which is characterized by a high-affinity binding for both GRP and bombesin. In human prostate cancer tissue, GRPR mRNA was reported to be detectable in more than 90% but its immunolocalizaition has not been reported. Therefore, in this study we immunolocalized GRPR in 51 human prostate cancer cases and correlated the findings with several clinicopathological parameters in order to better understand the function and regulation of GRPR in human prostate cancer. GRPR was immnolocalized in carcinoma cells and their values were significantly associated with Gleason score and immunoreactivity of estrogen receptor βcx (ERβcx) that is one of splicing variants of ligand dependent transcription factor, ERβ, and considered to be prognostic factor of prostate cancer patients. The amounts of GRPR and ERβcx mRNA in three prostate cancer cell lines PC-3, DU-145 and LNCaP evaluated by quantitative RT-PCR (qPCR) analysis were also significantly correlated. In addition, we established stable transformants of prostate carcinoma cell line PC-3 introduced with ERβcx, and confirmed that GRPR mRNA was induced in ERβcx over-expressing PC-3 cells by qPCR analysis. These results also suggest that ERβcx contributes to prostate cancer development possibly through mediating GRPR expression in carcinoma cells.