The cerebellum and inferior olive of adult homozygous leaner mutant mice (tgIa/tgIa) were examined using anti-vitamin D-dependent calcium binding protein immunohistochemistry, and Nissl staining. The immunohistochemical staining revealed that cerebellar Purkinje cell loss in leaner is restricted to alternating saggital compartments of the cerebellar cortex. The absence of Purkinje cells from specific sagittal zones of the cerebellar cortex apparently results in a loss of immunochemical staining of Purkinje cell axons and terminals from specific regions of the leaner cerebellar nuclear complex. A specific pattern of atrophy was also observed in the leaner inferior olive.