In the last six years Genome Wide Associations Studies (GWAS) have identified over 150 loci that contribute to bone mineral density or fracture risk. These loci have been the basis for identifying molecular pathways that contribute to bone phenotypes and identified potential drug targets. In the future this data might also be used to inform diagnosis and risk stratification utilizing the genetic burden  that predisposes individuals to disease. In this talk we will discuss the fundamentals of GWAS, how these studies the powered and the correct interpretation of results.