We conducted a study to determine whether a recently described restriction fragment length polymorphism in the vitamin D receptor gene (VDR-RFLP) predicts bone mineral density (BMD) in unrelated, premenopausal women as well as to determine the racial contribution to any genotypic influences on BMD. White (n = 83) and black (n = 72) women between 20 and 40 years of age were genotyped based on the presence (b) or absence (B) of a BsmI restriction enzyme site in the VDR gene, and BMD in the lumbar spine and femur neck was determined for each subject. There were 16 BB, 73 Bb, and 66 bb women. No significant difference was observed in genotypic distribution between the racial groups. The interaction of race by genotype on age- and body mass index (BMI)-adjusted BMD was not significant at either site. Age- and BMI-adjusted BMD was higher in black women at the spine (by 7.2%, p = 0.046) and femur neck (7.3% higher, p = 0.004). In the group as a whole, mean BMD in the femur neck was lower in the BB women that the bb (by 8.1%, p = 0.034) or Bb women (by 9.3%, p = 0.015) after controlling for age, BMI, race, and the race by genotype interaction. Adjusted lumbar spine BMD was lower in the BB women than the Bb women (6.4% lower, p = 0.036) in the group as a whole. No difference were detected between Bb and bb women at either site. A similar pattern of low BMD at the femur neck and the lumbar spine was seen in BB women of both races.(ABSTRACT TRUNCATED AT 250 WORDS)