Matrix metalloproteinase-9 (MMP-9) is implicated in bone remodeling. A - 1562C--> T polymorphism in the promoter of the MMP-9 gene (MMP9) has been shown to influence gene transcription. The possible relation of this polymorphism to bone mineral density (BMD) was examined in 1,114 Japanese men and 1,087 women. BMD for the total body, lumbar spine, femoral neck, trochanter, or Ward's triangle was significantly lower in the combined group of men with the CT or TT genotypes or in men with the CT genotype than in those with the CC genotype. No significant differences in BMD among MMP9 genotypes were observed in premenopausal or postmenopausal women. The -1562C-->T polymorphism of MMP9 was thus associated with BMD in Japanese men.