Five parallel anatomic circuits link regions of the frontal cortex to the striatum, globus pallidus/substantia nigra, and thalamus. The circuits originate in the supplementary motor area, frontal eye fields, dorsolateral prefrontal region, lateral orbito-frontal area, and anterior cingulate cortex. Open loop structures that provide input to or receive output from specific circuits share functions, cytoarchitectural features, and phylogenetic histories with the relevant circuits. The circuits mediate motor and oculomotor function as well as executive functions, socially responsive behavior, and motivation. Neuropsychiatric disorders of frontal-subcortical circuits include impaired executive function, disinhibition, and apathy; indicative mood disorders include depression, mania, and lability. Transmitters, modulators, receptor subtypes, and second messengers within the circuits provide a chemoarchitecture that can inform pharmacotherapy.