The neuroanatomical and neurophysiological data that have been obtained from experimental primates are converging on a framework for understanding the prefrontal influence on motor output. The framework isolates internally memory-based functions from externally guided sensory-based functions, identifies the internally-based functions with prefrontal circuits, the sensory-based functions with premotor circuits, and integrates the specializations of prefrontal, premotor and subcortical structures in the control of motor acts.