The cerebral cortex is interconnected with two major subcortical structures: the basal ganglia and the cerebellum. How and where cerebellar circuits interact with basal ganglia circuits has been a longstanding question. Using transneuronal transport of rabies virus in macaques, we found that a disynaptic pathway links an output stage of cerebellar processing, the dentate nucleus, with an input stage of basal ganglia processing, the striatum.