In order to explore the genetic constitution of a high bone mass phenotype, our aims were, first, to establish the prevalence of HBM in the BARCOS (BARCelona OSteoporosis) cohort of postmenopausal Spanish women; second, to determine whether any of the HMB cases carried LRP5 or DKK1 mutations that could explain the phenotype; and third, to assess whether the HBM cases were carriers of a low number of risk alleles of 55 autosomal GWA-identified BMD loci. Here, LRP5 is linked to osteoporosis.