EEG/closed-circuit television long-term monitoring was used as a definitive diagnostic tool to identify and characterize 25 patients with pseudoepileptic seizures and a similar group of subjects with epilepsy, confirming the value of the procedure. The groups did not differ with respect to intelligence, neuropsychological impairment, or incidence of potential etiological factors for seizures. Scores on the Minnesota Multiphasic Personality Inventory (MMPI) and the Hypochondriasis, Hysteria, and Schizophrenia Scales were significantly higher for the pseudoepileptic group than for the other subjects. As a whole, the former patients exhibited an MMPI profile pattern frequently seen in the conversion form of hysteria. A set of three rules derived from the MMPI profiles was used to classify the patients correctly in 80-90% of cases. As evaluated by the Washington Psychosocial Seizure Inventory, psychosocial problems of patients with pseudoepileptic seizures were more severe in certain areas, and appeared to reflect early family background problems and inappropriate management of their disorders.