Leptin is detected in sera and leptin receptors are expressed in the cerebellum of mouse embryos,suggesting roles of leptin in the cerebellar development. We here injected leptin into the lateral cerebralventricle of leptin receptor-deficient db/db and wild-type mouse embryos and examined the effects on cerebellar development. Leptin was injected on embryonic day（E）14, and the embryos were let to develop by exo utero method till E16 when the cerebellum was examined. Cerebellar volume, number of Math1-immunopositive progenitor cells of granule cells in the external germinal cell layer（EGL）did not differ significantly between db/db and wildtype. However, calbindin-positive Purkinje cells in the Purkinje cell layer（PCL）of db/db tended to be fewer in number and appeared less differentiated than those in wild-type. These results suggest that leptin may not have effect on EGL cells but may promote migration and/or differentiation of progenitors of Purkinje cells in PCL.