There are approximately three signature behavioral/cognitive syndromes that occur after damage to prefrontal cortex and its circuitary. First, damage to the dorsolateral prefrontal circuit causes executive dysfunction. These patients have difficulty in generating hypotheses and flexibility in maintaining and shifting sets as required by changing task demands. Second, damage to the orbitofrontal circuit causes disinhibited, irritable and labile behavior. This type of lesion also results in imitation and utilization behavior. Unlike patients with dorsolateral damage, these patients may not have executive impairments. Thirdly, damage to the medial frontal/anterior cingulate circuit causes akinesia, apathy and unconcern. Of course, patients may have damage to more than one of these frontal circuits, leading to a combination of clinical deficits. Unfortunately, these deficits may be hard to quantify on standard neuropsychological tests and may only be evident in real-life situations. This paucity of "objective" findings may lead to overlooking the possibility of damage to the frontal lobes in some patients. The frontal lobes may be less "hard-wired" than other cortical areas. They may act as an orchestrator for integrating other cortical areas and for calling up behavior programs that are appropriate for the context. Although this article is intended to outline a number of apparent frontal lobe functions, it is obvious that the functions of this massive and phylogenetically novel prefrontal cortex are complex, interrelated and as yet incompletely understood.