The vestibulo-ocular reflex has been used extensively for study of the neural mechanisms of learning that is dependent on an intact cerebellum. Anatomic, physiologic, behavioral, and computational approaches have revealed the neural circuits that are used to generate the vestibulo-ocular reflex and have identified two likely sites of plasticity within those circuits. One site of plasticity is in the vestibular inputs to floccular target neurons, which are located in the vestibular nuclei and receive monosynaptic inhibition from Purkinje cells in the floccular complex of the cerebellar cortex. The other site of plasticity is in the vestibular inputs to Purkinje cells in the floccular complex, possibly in the cerebellar cortex. After reviewing the evidence that supports these conclusions, I consider a number of observations showing that the dynamics of neural circuits or cellular mechanisms play important roles in learning in the vestibulo-ocular reflex.