This study examined the association between bone mineral density (BMD) and a T/C polymorphism in the first of the two initiation 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 codon and the f allele its presence. The FokI genotype was determined in 124 postmenopausal osteoporotic French women who were 45-90 years old. The distribution of FokI genotypes in the osteoporotics did not differ significantly from that found in a control group. There were no significant differences by FokI genotype groups in our 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 significantly lower BMD at the femoral neck than FF and Ff subjects. This suggests that the ff genotype of the VDR gene correlates with decreased BMD at the femoral neck in French postmenopausal women.