Focal segmental glomerulosclerosis (FSGS), the leading glomerular cause of the nephrotic syndrome among African Americans, is typically associated with edema, proteinuria, hypertension, microscopic hematuria, and renal insufficiency. Recent studies suggest that either the incidence of FSGS has increased or an increased number of biopsies of African American patients have made the diagnosis more common. The collapsing variant of FSGS, which occurs more commonly in African Americans than in whites, carries an especially poor prognosis with respect to renal survival. Although the pathogenesis of FSGS is not well understood, the fact that it frequently recurs early after transplantation has led to speculation that patients with FSGS may have a circulating factor that leads to increased glomerular permeability. There are no randomized control trials of treatment regimens for FSGS. Steroids, alkylating agents, and cyclosporin have all been used with variable results to treat FSGS.