Over a ten year period 105 children with a histological diagnosis of a mesangial proliferative glomerulonephritis were diagnosed. Patients were divided into two groups according to their clinical presentation at the time of diagnosis. Ninety two children presented with nephrotic syndrome (NS) of whom 82 received steroid therapy. No response was observed in 26 children and in 56 remissions were short in duration and subsequent relapses were frequent. Eighty nine children with the nephrotic syndrome were treated with cyclophosphamide (CP) of whom 26 had a steroid resistant NS, 53 were steroid dependent and 10 were previously untreated. Eighty four entered remission with a mean duration of 46 months. Only 5 children did not respond to treatment with CP. No correlation could be found between the results of therapy and the degree of morphological changes on examination of renal biopsy. The second group consisted of 13 children presenting with a persistent nephritic syndrome and or proteinuria. These children were untreated and no progression of renal disease was observed after several years follow up.