Notch signaling pathway may play an important role in the development of the olfactory epithelium (OE). To elucidate whether the Notch signaling pathway mediates the developmental processes in the developing OE. The expression of Notch1 and Hes5 in the developing OE of mice with ages ranging from embryonic day (E) 11 to postnatal day (PN) 14 was examined. As detected by in situ hybridization, Notch1 was expressed in scattered cells located in the basal portion of the embryonic OE and later in the cell layer adjacent to the basal lamina from E11 to PN14. Hes5 was expressed in scattered cells located in the basal portion of the embryonic OE from E11. However, at the late embryonic stage, the number of Hes5-positive cells decreased and after birth distinct Hes5-positive cells were not observed in the OE.