IgAN is the most common type of glomerulonephritis worldwide, and is found more in men and distinctly less in blacks. It presents with macroscopic hematuria in about 40 to 45% of patients, with microscopic hematuria and proteinuria in about 35 to 40%, and with nephrotic syndrome or acute renal failure in the remainder. The diagnosis continues to rely on the finding of the dominant or codominant mesangial deposition of IgA on immunohistologic examination of the kidney. No blood or urine test is sufficiently reliable for diagnosis. While the pathogenesis remains unknown, accumulating evidence suggests that polyclonal stimulation of immunoglobulins perhaps coupled with structural abnormalities of IgA play pivotal roles. These defects may account for the variety of autoantibodies detected in patients with both IgAN and HSP. While IgAN has an indolent course, about 30% of patients will reach ESRD after 20 years, particularly in those who present with hypertension, heavy proteinuria or renal insufficiency. At present, therapy is disappointing, but immunoglobulin supplementation and newer agents that interrupt the pathways of mesangial proliferation and sclerosis hold promise for the future. Kidney transplantation has shown excellent allograft survival.