Anatomical connections between the frontal lobes and basal ganglia have long suggested joint participation in behavioural operations. Early experiments with nonhuman primates and patients are reviewed, followed by current research investigating the specific cognitive routines at risk in Parkinson disease. An hypothesis regarding the functional contribution of the basal ganglia to the frontostriate system is offered. The basal ganglia are considered to set limits on the context within which mental and motor events occur. It is argued that the nature of such processing is subcognitive.