Androgen deprivation causes a reduction of blood flow in the prostate gland that precedes temporally apoptosis of the epithelium. The acute response of prostate endothelial cells to androgen deprivation suggested they represent a primary target for androgen. However, rat prostate endothelial cells were reported not to express androgen receptor (AR) and the role of the androgen axis in human prostate endothelial cell (HPEC) homeostasis was poorly characterized. In this study, AR expression was detected in HPEC in vivo in clinical specimens of benign prostate and prostate cancer, and AR function as a transcription factor was demonstrated in HPEC in primary xenografts of human benign prostate tissue transplanted into SCID mice by intravenous administration of adenoviral MMTV-driven luciferase expression vector. AR expression and functionality was maintained in vitro in primary cultures of HPEC that co-expressed CD31, CD34, von Willebrand Factor, ICAM, VEGFR1 and VEGFR2, but did not express PSA. AR expression in primary cultures of HPEC isolated from surgical specimens of benign prostate was validated using RT-PCR, cDNA sequencing, immunocytochemistry, and Western blot analyses. Scatchard analyses demonstrated a single ligand-binding site for R1881 in primary cultures of HPEC, with dissociation constant (K_d) of 0.25 nM, and AR-mediated transcriptional activity was demonstrated using adenoviral MMTV-driven luciferase reporters. Dihydrotestosterone increased proliferation in primary cultures of HPEC in a dose-dependent manner without modulating endothelial tube formation in Matrigel. Therefore, human prostate endothelial cells express functional AR, and androgen plays a direct role in modulating human prostate endothelial cell biology.