The vitamin D receptor (VDR) has been detected in breast tumor cells. We tested the hypothesis that VDR gene polymorphism might influence the outcome of women affected by breast cancer. A total of 88 breast cancer patients were recruited: 50 women were affected by newly diagnosed breast cancer whereas 38 women suffered from relapsing disease. The individual genetic pattern for VDR was evaluated by DNA extraction followed by PCR amplification of the VDR gene, and digestion with the restriction enzyme BsmI. In 167 healthy women, participating in the osteoporosis prevention trial and being used as a control, we detected 121 Bb heterozygotes (72%), 26 homozygotes for the bb alleles (16%), and 20 homozygotes for the BB alleles (12%). In the newly diagnosed breast cancer group the occurrence of Bb patients was 58% (29/50); bb patients represented 22% (11/50), and BB cases were 20% (10/50). The VDR frequency distribution in the control and primary disease patient groups was not statistically different. In the metastatic cancer group, the prevalence of the bb genotype (14/38; 37%) was double the percentage of control subjects, whereas the percentage of BB women with metastases was half the control group (2/38; 5%). Women who were homozygous bb appeared to have almost a four times higher risk of developing metastases than BB women. Whatever the molecular mechanisms underlying the VDR effects in cancer cells, we believe that the VDR gene polymorphism may represent an important determinant in the evaluation of women affected by breast cancer and might help design targeted therapy.