The localization of PKC gamma mRNA expression during the maturation of rat cerebellum has been studied by in situ hybridization. We found a transient expression over the granule cell layer and persistent high expression in the Purkinje cells during postnatal development. Expression in granule cells appeared as early as postnatal day 5 over the external granule cell layer, when Purkinje cells are multiply innervated by climbing fibres in contrast to their mono-innervation in the adult. As the regression of the poly-innervation during the following weeks is known to require granule cell input, our findings suggest that the PKC gamma expression over the migrating granule cell layer is linked to the process of selective stabilization of synapses during the maturation of the cerebellum.