We report on a patient with membranoproliferative glomerulonephritis (MPGN) type III, whose repeated renal biopsies show evolution from a type I-like pattern to a type III pattern of immune complex formation over a 1-year period. Based on the development of experimental in situ immune complex glomerulonephritis, we discuss possible mechanisms for the formation of subepithelial deposits in type III MPGN with reference to an experimental in situ immune complex model of glomerulonephritis.