Each of the four stages of membranous glomerulonephritis (MGN) has a characteristic ultrastructural appearance. This report described four children with another distinctive pattern of MGN, which we propose to call segmental membranous glomerulonephritis (SMGN). In all cases there were segmentally distributed subepithelial or intramembranous electron-dense or electron-lucent deposits and prominent spikes. Less than 50% of capillary loops per glomerulus were affected. Granula deposits of IgG were identified by immunofluorescence microscopy, but deposits were either absent or less intensely fluorescent in repeated biopsies. All four patients had proteinuria. Three patients have normal creatinine clearances with either diminished proteinuria (one patient) or no proteinuria (two patients) after a mean follow-up of ten years. The fourth patient died of an unrelated cause. The evolution of MGN and SMGN is discussed and it is proposed that SMGN represents partial resolution of MGN.