The globus pallidus (GP) of the mouse was studied by the rapid Golgi silver impregnation method. The GP was composed of large and medium-sized neurons. The large neurons had stellate cell bodies with a mean diameter of 25 micron by 28 micron and five to seven primary dendrites. The somata of the medium-sized neurons were spindle or fusiform in shape, measured 19 micron by 27 micron in average and emitted three to five primary dendrites. The large neurons were located mainly in the central part of the GP, whereas the medium-sized neurons were observed in the peripheral part of the GP. Some GP neurons extended their dendrites into the caudatoputamen complex, sublenticular region or internal capsule. The axons of the GP neurons were seen most frequently to course medially or mediocaudally and to enter the internal capsule or fiber bundles traversing the GP; they were rarely observed to run laterally and to travel into the caudatoputamen complex. Some axons of the GP neurons were also observed to emit intra- or extra-nuclear collaterals extending into the sublenticular region. Four groups of afferent fibers to the GP were observed; (1) fibers descending within the internal capsule or caudatoputamen complex to terminate or to give axon-collaterals to the GP; (2) fibers ascending within the internal capsule or fiber bundles traversing the GP to enter the GP from its medial aspects; (3) fibers traversing the internal capsule laterally to terminate in the GP; and (4) fibers running dorsally through the sublenticular region to terminate in the GP. In addition to these four groups of afferent fibers, terminal branches were seen to arise numerously from many fibers running through the GP.