Associations between polymorphisms of the osteoprotegerin gene (OPG) and bone mineral density (BMD) have been studied by several research groups, but results are mixed. Accordingly, the authors performed a meta-analysis on studies of associations between OPG polymorphisms and BMD. Appropriate studies were identified using MEDLINE and by manual searching. A total of eight separate comparisons were considered in this meta-analysis. Individuals with the GG genotype of G1181C were found to have a significantly lower mean lumbar BMD than subjects with the CC genotype (WMDs -0.051 g/cm(2), 95% confidence interval -0.079--0.023, P < 0.001), and similar results were obtained in European and Asian populations. In contrast to G1181C, no association was found between the A163G and T950C polymorphisms and lumbar BMD. In terms of femoral neck BMD, the GG genotype of G1181C was associated with a significantly lower BMD than the CC genotype in Europeans but not in Asians. Total hip BMD was lower for the GG genotype of G1181C than for the CC or GC genotypes in Europeans. A difference in total hip BMD was found between the AG and GG genotypes of the A163G polymorphism by meta-analyses in Europeans, but no differences were found between the genotypes of the T950C polymorphism and total hip BMD in Europeans. Summarizing, the present study demonstrates that the OPG G1181C polymorphism is associated with lumbar BMD in Europeans and Asians, and with femoral neck and total hip BMD in Europeans only.