This review summarizes the literature data and the results of the authors' own investigations on morphology, neurochemical specialization, and spatial organization of unipolar brush neurons (UBN) in the cerebellar cortex and brainstem cochlear nuclei. UBN represent excitatory interneurons with a single dendrite that forms a compact brush-like branching in its terminal part. They are distributed non-uniformly in the granular layer of the cerebellar cortex and are localized predominantly in its vestibular areas. UBN synthesize glutamate, calretinin, contain metabo- and ionotropic glutamate receptors. Dendritic brush of UBN forms the giant synapses with the rosettes of glutamate- and cholinergic afferent mossy fibers. Axons of UBN form intracortical system of mossy fibers, which, by forming rosettes and glomeruli, make contacts with dendrites of similar cells and those of the granular cells. In the chain of inerneuronal communications, UBN may be regarded as the intermediate link, which amplifies the excitatory effect of the afferent mossy fibers upon granular cells of the cerebellar cortex and brainstem cochlear nuclei.