Previous studies suggested a relation between polymorphism of the vitamin D receptor (VDR) gene and bone mineral density (BMD) at perimenopausal age. To enlighten the possible association of the VDR gene polymorphism and BMD, we studied young (20-29 years) adults whose BMD provides a measure of their maximal bone mass. After sequencing the DNA regions flanking the polymorphic BsmI site, we set up a specific solid-phase minisequencing technique to assay this allelic variation. BMD values were adjusted for age, sex, weight, physical activity, smoking, and calcium intake. Young subjects homozygous for the b allele (BsmI site present) had a significantly higher BMD in lumbar spine and femoral neck than those homozygous for the B allele (BsmI site absent). This data shows that the BsmI polymorphism of the VDR gene is associated with peak bone mass. The implication of this result regarding the prevention of osteoporosis deserves further attention.