Osteoporosis is a common disorder with a strong genetic component. Our aim was to evaluate the correlation of the vitamin D receptor gene intron 8 BsmI polymorphism with bone mineral density (BMD) and their relationship to osteoporosis. We determined the vitamin D receptor gene intron 8 BsmI polymorphfsm using polymerase chain reaction-based restriction analysis in 171 postmenopausal Chinese women in Taiwan. The polymorphism was detected using the restriction enzyme BsmI, where the B allele indicated absence of the cuttable site and the b allele its presence. BMD of the lumbar spine and proximal femur were measured using dual-energy X-ray absorptiometry. The allelic frequencies for postmenopausal Chinese women in Taiwan were 12.3% for B and 87.7% for b in BsmI restriction fragment length polymorphisms. The prevalence of each genotype in the study population was: 6.4% BB, 11.7% Bb and 81.9% bb. The three genotypic groups differed significantly in BMD at the lumbar spine and the femoral neck. These differences corresponded to significant gene-dose effects at the lumbar spine and femoral neck (p<0.001 for both sites). The relative risk for the development of osteoporosis was about 2-3 times as great as that predicted by the differences between genotypes in BMD, and remained significant even after adjustment for age, height and weight. The vitamin D receptor gene intron 8 BsmI polymorphism is associated with reduced BMD and predisposes women to osteoporosis.