Membranous nephropathy has an incidence of approximately 1 case per 100,000 persons per year, and its phenotype has been clearly defined on the basis of histologic features. Recognized as a clinicopathological entity in the 1950s, membranous nephropathy is the most common diagnosis in adults with the nephrotic syndrome. Roughly one fourth of the biopsies performed in patients with the nephrotic syndrome show membranous nephropathy, which is among the glomerulonephritides that lead to end-stage renal disease. One of its hallmarks is the presence of glomerular deposits that typically contain immunoglobulin and complement components.