Neuroanatomic comparisons between rodents and humans are complicated by the phylogenetic distance between the species. Rodent and human brains differ markedly in size and organization, particularly in the functional and structural arrangement of the cerebral cortex. This chapter highlights major differences in the nervous system between rodents and humans, emphasizing divergence in their gross and microscopic anatomy as well as their regional organization; some functional variations are also noted. Major brain regions discussed are, from rostral to caudal, the cerebral cortex, basal ganglia, hippocampus, diencephalon (thalamus and hypothalamus), mesencephalon (midbrain), cerebellum, and brain stem (pons and medulla). Ancillary brain structures described are the pineal and pituitary glands, circumventricular organs, ventricular structures (choroid plexus and ependyma), and brain vasculature. Spinal cord and the peripheral nervous system are also examined.