Three sibs born to consanguineous parents had congenital nephrotic syndrome, microcephaly, and psychomotor retardation. Pathology of the kidneys showed diffuse mesangial sclerosis with deposits of IgG and C3 in the mesangium and glomerular basement membranes. All three children died before the age of 3 years. Of 19 published cases of children with the association of congenital nephrotic syndrome and microcephaly, only four had histological evidence of diffuse mesangial sclerosis, and two of their sibs probably had the same disease. The association of nephrotic syndrome owing to congenital diffuse mesangial sclerosis, microcephaly, and mental retardation appears to be a distinct syndrome with an autosomal recessive mode of inheritance.