Vitamin D receptor (VDR) genotype was determined in 66 Japanese patients with primary hyperparathyroidism (pHPT). In contrast to previous report showing an association between VDR genotype bb and the development of pHPT in a Swedish population, we did not find any differences in the frequencies of the VDR genotypes between pHPT and the control. The bone mineral density in the radius was significantly lower (Z score, -1.723 +/- 1.819) in bb genotype than in BB/Bb genotype (+0.255 +/- 2.344) in pHPT patients. Based on the fact that PTH requires vitamin D3 to take effect on calcium mobilization from bone, it is possible that VDR polymorphism may influence the PTH action on bone.