Over the past few years, considerable advances have been made in our understanding of the molecular pathomechanisms of human membranous nephropathy, inspired by studies of Heymann nephritis, a faithful experimental model of this disease. This research led to the identification of neutral endopeptidase, the M-type receptor for secretory phospholipase A(2) (PLA(2)R1) and cationic bovine serum albumin as target antigens of circulating and deposited antibodies in alloimmune neonatal, adult 'idiopathic' and early-childhood membranous nephropathy, respectively. A genome-wide association study has provided further evidence for a highly significant association between PLA2R1 and HLA-DQA1 loci and idiopathic membranous nephropathy in patients of white ancestry. Additional antibody specificities for cytoplasmic antigens have also been identified, but their pathogenic role is uncertain. The time has come to revisit the spectrum of membranous nephropathies based on the newly identified antigen-antibody systems that should be considered as molecular signatures of the disease and that challenge the uniform histological definition. These signatures will soon have a major impact on patient care.