The distribution of gangliosides in serial cryostat sections of area CA2 of the ox hippocampus cut parallel to the ventricular surface and of a cerebellar folium cut parallel to the pial surfaces have been determined utilizing a fluorimetric method for analysis of N-acetylneuraminic acid. Wide differences in the ganglioside content, even in adjacent sections, were found within the various laminae, particularly in the molecular layers of the hippocampus and cerebellum. The variations in ganglioside concentrations largely disappeared when sections were cut so as to include all the laminae in one section. Average ganglioside concentrations per unit of dry weight were highest in the granular cell and molecular layers of the cerebellum, but in the hippocampus the highest values were obtained just below the stratum granulare of the fascia dentata. The results indicate that gangliosides are not uniformly distributed throughout the neuron but are concentrated in regions densely supplied with synaptic endings on both cell bodies and dendrites.