The androgen receptor (AR) is widely expressed in human tissues and has biological function in many male and female organs. In particular, the AR plays a critical role in the biology and pathology of the prostate gland. AR activity inhibits breast growth and has pleiotropic actions in breast cancer that are subtype-dependent. Expression of AR splice variants (ARVs) and their role in prostate carcinogenesis has been elucidated in recent studies. We hypothesised that ARVs are also expressed in breast cancers and other hormone sensitive tissues. Herein, the expression of five previously identified ARV transcripts with documented transcriptional capacity (AR-V1, -V3, -V4, -V7, and -V9) was examined in 6 breast (MFM223, MDA-MB-453, MDA-MB-231, ZR75