This study describes the distribution and relative level of labeling of binding sites for corticotrophin releasing factor (CRF) in the postnatal mouse cerebellum. At birth low levels of labeling are present throughout the cerebellum. However, this labeling is most densely distributed in the caudal and lateral aspects of the cerebellum. By P3 CRF binding sites are present throughout the cerebellum, although the greatest level of labeling is in the posterior lobe of the vermis, especially lobules IX and X; this correlates with the early differential pattern of CRF distribution in cerebellar afferents within these same lobules. At P10, the adult pattern of distribution and level of labeling begins to emerge. The presence of CRF and CRF binding sites at birth, and during postnatal growth, suggests that this peptide could play a role in the regulation of developmental events within the cerebellum.