Previously we showed that protein kinase C (PKC) isozymes (types I, II, and III) have distinctive neuronal localizations in cerebellum. In the present study, we followed the different appearances of these isozymes during the postnatal development of cerebellum. By immunoblot analysis, type I PKC was found to be low within 2 weeks after birth; an abrupt increase was observed between 2 and 3 weeks and leveled off afterwards. By immunofluorescent staining, the type I PKC-specific antibody recognized the cell bodies and dendrites of Purkinje cells. The increase of this isozyme between 2 and 3 weeks of age correlates with the spreading of Purkinje cell arborization, at which time bulk of synaptogenesis between dendritic spines and axons of granule cells occurs. Both type II and III PKCs were present in granule cells. At birth, the level of type II PKC was relatively high compared to that of type III PKC, and the type II PKC-specific antibody stained the granule cell precursors in the external layer more heavily than did the type III PKC-specific antibody. The level of type II PKC declined slightly after birth and increased again at one week and plateaued after three weeks, whereas that of type III PKC increased gradually until leveling off after three weeks. Throughout the development, the type III PKC-specific antibody also stained the cell bodies of Purkinje cells but not their dendrites. These results demonstrate that the developmental expression of PKC isozymes is under separate control, and their distinct cellular and subcellular localizations suggest their unique functions in the cerebellum.