Nine case descriptions illustrate the three major prefrontal syndromes seen in clinical practice: disorganized type, disinhibited type, and apathetic type. A mixture of symptoms from each subtype is usually seen, but dysfunction in one prefrontal system often dominates. A careful history and examination are essential for accurate diagnosis. A complete history can rarely be elicited from the patient alone. Structural brain imaging, especially MRI, and neuropsychological testing are key to the diagnostic workup. EEG, video-EEG, and functional brain imaging can be valuable in the evaluation of possible partial complex seizures of frontal lobe origin and other atypical frontal lobe disorders. Effective treatment requires educating the patient and the family about the illness and modulating environmental factors that influence the patient's behavior. Judicious use of psychoactive medication may be helpful, but adverse effects are common.