The prolactin concentration profile over 24 hours was determined in three men, aged 19, 27 and 43 years, who suffered from treatment-resistant complex-partial and (or) grand mal seizures of frontal lobe origin. All three patients were examined in the course of preoperative epilepsy diagnosis, the seizures being classified by video-EEG recordings, including subdural and sphenoidal foramen ovale electrodes. Seizures were recorded in all three patients (4 grand mal; 2 complex-partial), each of them followed by a rise in serum prolactin concentration (over 700-mu-U/ml). These findings contradict the theory that prolactin concentration rises only after temporal, not after frontal seizures. Knowing the postseizure serum prolactin concentration may help to distinguish frontal epileptic from psychogenic seizures.