Therapy with prednisone in an alternate day regimen over periods of 1.5 to 15 years in 27 children with membranoproliferative glomerulonephritis (MPGN) resulted in survival of 89% at 15 years after onset as compared with 50% survival at 6-12 years in the reports of other investigators. Therapy started, on the average, 1.5 years after onset in the 23 children with a good response and 5.2 years after onset in the 4 who developed irreversible renal failure. In most, clinical manifestations have diminished or, in many of those with Type I MPGN, disappeared. Glomerular scarring often increased with therapy but did not necessarily compromise function. Changes in morphology of functioning glomeruli varied with the type. In Type I, subendothelial deposits disappeared. In Types I and II, capillary walls became thinner and more capillary lumens were visiable. In Type III, glomerular morphology did not significantly change although clinically most of the patients have improved or are stable.