The distribution of corticotropin-releasing factor (CRF), the development of CRF-binding sites, and the age at which application of CRF elicits a physiological response have been described previously in the postnatal mouse cerebellum. The intent of the present study was to determine the cellular and subcellular distribution of the CRF type 1 receptor (CRF-R1) in the vermis of the postnatal mouse cerebellum and to correlate these data with those presented in previous studies. On P0, CRF-R1 is present in the apical processes of migrating Purkinje cells. Between P0 and P8, CRF-R1 immunostaining is confined to a supranuclear position in Purkinje cell bodies. Between P9 and P14, the receptor immunolabeling circumscribes Purkinje cell nuclei and extends into their primary dendrites. An adult-like distribution is achieved between P16 and P21. Between P0 and P14, the CRF-R1 antibody also labels processes of migrating GABAergic interneurons that are directed toward the pial surface. By P12, labeling begins to circumscribe the nucleus of GABAergic cells in the internal granule cell layer. Finally, astrocytic processes in the white matter, as well as radial glial processes, show focal labeling with the CRF-R1 antibody beginning at P3 and throughout postnatal development. A previous study demonstrated that CRF does not elicit a physiological response in Purkinje cells until P9. This observation, together with the data presented in this study, suggests that the binding of CRF to the type 1 receptor may be involved in regulating the development of cerebellar neurons and glia immediately after birth, before CRF assumes its function as a neuromodulator later in postnatal development and in the adult.