The differential expression of specialized voltage-gated potassium (Kv) channel subtypes in the nervous system probably reflects the wide range of functions. Although there have been previous reports in the cellular and subcellular localizations of various Kv mRNAs and proteins, the comprehensive study described here is the first in which the expression of six Kv1 channel subunits have been directly compared in the rat basal ganglia. In the present study, we have found that staining patterns of the six Kv1 channel subunits overlap in some areas of the basal ganglia, but each has a unique pattern of expression. It was noted that Kv 1.4 subunit had a strikingly high level of expression in the globus pallidus compared to the caudate-putamen. This distinct distribution formed the clear demarcations between caudate-putamen and globus pallidus. The dot-like staining pattern of Kv1 subunits was observed through the accumbens nucleus. Strong staining for Kv1.4 was observed in the cerebral peduncle, not in the subthalamic nucleus. In the substantia nigra, immunoreactivity for Kv1.4 subunit was prominent in the pars reticulata of the substantia nigra. The staining intensity for Kv1.2 was high in the pars compacta of the substantia nigra. Our immunohistochemical results may support the notion that the formation of heteromultimeric Kv channels possibly represents an important contribution to the generation of Kv channel diversity in the brain, especially in the basal ganglia.