Mutations in the chloride channel 7 gene (CLCN7) cause osteopetrosis, and polymorphisms of CLCN7 in the non-disease allele are associated with penetrance of the autosomal dominant osteopetrosis (ADO) phenotype. Studies have also shown an association between CLCN7 polymorphisms and bone mineral density (BMD) in women. However, there is no study to date that has examined whether CLCN7 polymorphisms underlie normal variation of peak BMD in healthy premenopausal white women and in white men.Six single nucleotide polymorphisms (SNPs) and one variable number tandem repeat (VNTR) polymorphism in the CLCN7 gene were genotyped. Association was tested between CLCN7 gene polymorphisms and both lumbar spine and femoral neck BMD. Healthy premenopausal white sisters (age 33.1+/-7.2, n=1692) and healthy white brothers (age 33.6+/-10.9, n=715) were studied.No significant association between CLCN7 gene polymorphisms and BMD at the lumbar spine or femoral neck was found in white women or white men.Genetic variation in the CLCN7 gene is not a major contributor to the variability in peak BMD at the femoral neck and lumber spine in healthy premenopausal white women and in white men.