Despite 31 years of clinical and laboratory investigation, the pathogenesis of IgAN remains largely enigmatic. However, it seems clear that IgA1 accumulates in the glomerular mesangia due to a systemic process rather than an abnormality intrinsic in the kidney. Based on recent studies, investigators have proposed a wide range of pathogenetic mechanisms: nonspecific attachment because excessive IgA1 is synthesized in a short or prolonged immune response, increased binding due to an IgA-specific receptor (perhaps with altered characteristics) on mesangial cells, and increased glomerular deposition because an abnormal structure of the antibody (particularly of the glycan moieties in the hinge region) allows it to escape its normal degradative pathways or facilitates binding to a receptor on mesangial cells. Whether one or more of these postulates fully explains IgAN remains to be determined. Until then, treatment of the many affected patients worldwide will continue to lack a disease-specific approach.