The motor circuitry of the basal ganglia is organized in parallel with basal ganglia circuits involved in oculomotor, associative, and limbic functions. These circuits comprise reentrant pathways that originate in various neocortical domains and pass through the basal ganglia before returning, by way of the thalamus, to select portions of the frontal lobe. Recent progress in characterizing the anatomy and physiology of these pathways has provided new insights into the pathophysiology of basal ganglia-related movement disorders and enhanced our understanding of the normal role of the basal ganglia in movement control and adaptive motor behavior.