The maturation of the intermediate cell of Lugaro, impregnated by classical silver methods, was studied on parasagittal sections of cerebellar vermis of newborn rat pups. Using morphological criteria characteristic of the adult cell type, immature Lugaro neurons can be recognized from the second part of the first postnatal week on. This implies that these cells differentiate at a much earlier age than previously inferred from studies using tritiated thymidine.