Focal segmental glomerulosclerosis (FSGS) and a related condition, collapsing glomerulopathy, are chronic renal diseases affecting the glomerular podocytes. Currently, over thirteen genetic mutations are associated with FSGS. We are interested in expanding our understanding of these and other genes that may cause FSGS and collapsing glomerulopathy. We will study individuals with affected family members. We will also study sporadic cases; the rationale for studying this population is that FSGS and collapsing glomerulopathy are significantly more common among individuals of African descent. The latter observation suggests that particular FSGS-susceptibility alleles may be more common among African Americans. In the present study, we are addressing the hypothesis that genetic variation contributes to the pathogenesis of idiopathic FSGS and collapsing glomerulopathy, both idiopathic and HIV associated variants.