The immunopathogenesis of IgA nephropathy remains uncertain despite intensive efforts by many investigators. An increasing awareness of regional and racial differences in prevalence and renal disease in relatives of patients with IgA nephropathy have suggested a possible genetically influenced mechanism in the pathogenesis of the disease. Several studies of families of patients with IgA nephropathy have shown apparent imbalances in the immunoregulation of the IgA immune system. Indeed, some family members with abnormal laboratory tests similar to their relative with IgA nephropathy exhibit clinical findings of glomerulonephritis. However, the necessity of an invasive renal biopsy procedure for the diagnosis renders a cause-and-effect conclusion difficult. Therefore, no serological or cellular marker can identify patients with IgA nephropathy or accurately screen family members. None the less, we believe that recent studies have strengthened the hypothesis for a genetically determined influence in the pathogenesis of IgA nephropathy in some patients.