Ganglioside N-acetylneuraminic acid (NANA) content and distribution and that of incorporated radionuclide from 1-[ 14C]glucosamine were investigated under conditions of normal development and after administration of 500 μg of cortisol at 1 day of age. Cortisol delayed significantly the rise in tissue concentration of NANA usually occurring between 2 and 20 days of age. Cerebellum was most severely affected and brainstem least. The incorporation of radionuclide was depressed during the developmental lag then increased beyond controls from 6 to 10 days, and was again below that of controls in cerebrum and brainstem at 20 days. Individual study of seven chromatographically distinct resorcinol-positive compounds indicated that cortisol treatment favored accumulation and labeling of the more polar gangliosides initially, but resulted at 20 days of age in an abnormal ganglioside pattern with less polar compounds present disproportionately.