The distribution and properties of synaptic inputs to cells in the medial vestibular nucleus was studied in decerebellated cats anesthetized with chloralose-urethan. Recording from single units was extracellular and all tracks were marked with fast green dye. Stimulation of the ipsilateral labyrinth fired 22% of the cells monosynaptically, 33% polysynaptically, and 13% mono- and polysynaptically. The cells fired included units with long axons projecting rostrally or caudally, as well as cells lacking such axons. The synapse between vestibular afferents and medial nucleus cells is a powerful one, similar to that at various other relay nuclei. Most monosynaptically driven cells were found in the rostral 60% of the nucleus, in agreement with anatomical findings. Some cells in the nucleus were fired, others inhibited, by stimulation of the contralateral labyrinth. The inhibitory pathway usually consists of a commissural cell and an inhibitory neuron, sometimes probably only of an inhibtory commissural cell. Ascending and descending excitatory pathways converged on some cells, and few of these had long axons.