Recent anatomical and physiological studies have shed new light on the functional organization of the basal ganglia and the contributions of these structures to movement. While the striatum receives input from the entire neocortex, this information appears to remain segregated in the basal ganglia along lines established at the cortical level. There appears to be, in the broadest sense, a maintained segregation of information relevant to motor and" complex" functions. The concept of segregated parallel subcortical loops subserving" motor" and" complex" functions is discussed. Single cell studies in the basal ganglia of behaving animals have revealed specific relations of neuronal activity to movements of individual body parts and a relation to specific parameters of movement, particularly direction, amplitude, and velocity. The pathophysiologic basis of akinesia tremor, rigidity, and diskinesias is discussed in light of recent findings.