Clinical and pathological findings in four Turkish infants with isolated diffuse mesangial sclerosis (DMS) are presented. All the patients were offsprings of consanguineous marriages and two had similarly affected sibs indicating an autosomal recessive inheritance. The onset of the nephrotic syndrome was at 7, 17, 11 and 3 months of age. They all died in a state of renal failure complicated by infections at the ages of 11, 33, 13 and 5 months. DMS was diagnosed at postmortem examination in all. Fluorescence-microscopical studies in all and an electron-microscopical study in one revealed nonspecific findings. The shorter survival in three of the cases was thought to be due to intervening infections. The variation of the clinical features along with the fluorescence and electron-microscopical findings are consistent with the previously mentioned heterogeneous aspect of DMS.