Background Osteoporosis is 3-fold more prevalent in HIV-infected individuals, compared to HIV-uninfected controls. Osteoporosis thus represents an important although incompletely understood metabolic complication in HIV-infected individuals. Bone mineral density (BMD) is a highly heritable trait in the general population (heritability, 60-90%). Genome-wide association studies (GWAS) of BMD have been published in 2007-2010 in the general population. The contribution of genetic factors to BMD has not been evaluated in HIV-infected individuals. Study Aims 1) to investigate the contribution of 57 SNPs to BMD in 600 SHCS participants with available DEXA scans. 2) to investigate the contribution of 57 SNPs to atraumatic fractures in 55 SHCS participants with atraumatic fractures and known fracture date. 3) to quantitatively assess the relative contribution of cumulative genetic background and pertinent non-genetic variables to BMD and atraumatic fractures. Study Design Study methodology will be similar to successfully published SHCS #570 projects (dyslipidemia, diabetes) and the ongoing coronary event project (MAGNIFICENT, SHCS #599). Effects of genetic and relevant non-genetic co-variables on BMD/fractures will be evaluated at the level of the individual participant and in the study population. Endpoints will be continuous (bone mineral density) and categorical (osteoporosis, fractures).