Vitamin D has anti-proliferative and proapoptotic effects on several cell types, including breast cancer cells. There have been no studies quantifying the expression of the enzyme 25-hydroxyvitamin D-1-alpha-hydroxylase (1alphaOHase), which converts 25-hydroxyvitamin D to its active metabolite, in breast tissue. We performed real-time RT-PCR to quantity 1alphaOHase and vitamin D receptor (VDR) mRNA in samples of breast cancer, adjacent non-cancerous tissue and normal breast tissue. 1alphaOHase and VDR mRNA were universally expressed, however, 1alphaOHase expression was significantly down-regulated in adjacent non-cancerous tissue from women with breast cancer in comparison to individuals without cancer. VDR was also up-regulated in breast tumours. The vitamin D axis expression in the breast suggests a role for its actions in normal tissue homeostasis and breast cancer pathogenesis. The decreased expression of 1alphaOHase in normal tissue from women with breast cancer may be important in their predisposition to the development of cancer.