This study examined the association between bone mineral density (BMD) and a T/C polymorphism in the first of two start (ATG) codons in the vitamin D receptor (VDR) gene. The polymorphism was detected using the restriction enzyme FokI, the F allele indicating absence of the first ATG and the f allele indicating the presence of the first ATG. The FokI genotype was determined in 124 postmenopausal osteoporotic French women who were 45 to 90 years old. The distribution of FokI genotypes in osteoporotics didn't differ significantly from that found in a group of French random blood donors. There were no significant differences by FokI genotype group in the total sample of osteoporotic women for age, years since menopause, height, weight, and BMD at lumbar spine and femoral neck. However, when only those patients under the age of 75 years are analysed (98 subjects, those with the ff genotype (10% of the population) had a significant lower BMD at the femoral neck than FF and Ff subjects. We conclude that the unfavourable ff genotype of the VDR gene correlates with decreased BMD at the femoral neck in French postmenopausal women.