Context: A major determinant of osteoporotic fractures is peak bone mineral density (BMD), which is a highly heritable trait. Recently, we identified significant linkage for hip BMD in pre-menopausal sister pairs at chromosome 14q (LOD score = 3.5), where the estrogen receptor (ESR2) gene is located. Objective: To determine whether ESR2 polymorphisms are associated with normal BMD variation. Design: Population-based genetic association study, using eleven single nucleotide polymorphisms (SNPs) distributed across the ESR2 gene. Setting: Academic research laboratory and medical center. Patients and Other Participants: 411 healthy men (age 18-61) and 1291 healthy pre-menopausal women (age 20-50) living in Indiana. Intervention(s): None. Main Outcome Measure(s): SNP genotype distributions and their association with BMD measured at femoral neck and lumbar spine. Results: Significant association of spine BMD was found with three SNPs in men and one SNP in women (p-value 0.05). The conditional linkage analysis using the ESR2 haplotypes showed that the ESR2 gene accounts for at most 18% of the original linkage. Conclusions: ESR2 polymorphisms are significantly associated with bone mass in both men and women. However, the ESR2 gene is not entirely responsible for our original linkage, and an additional gene(s) in chromosome 14q contributes to the determination of BMD.