This short review deals with observations on the gross morphology and internal structure of the human cerebellum, and with studies of cerebellar fiber connections in non-human primates. Attention is focussed on its gross anatomy, the zonal organization of the primate cerebellum, the brain stem, thalamic and cortical connections of the cerebellar nuclei and on the cortico-ponto-cerebellar pathway. The presence of important reciprocal nucleo-mesencephalo-olivary loops as part of the circuitry of the dentate and globose (posterior interposed) nuclei and their absence among the connections of other cerebellar nuclei is emphasized.