Investigations demostrated that LHM produces EEG effects which are characterized by a decrease of very slow and very fast activities and increase of 8-20 cps waves in the primary wave measurements, and decrease of slow and increase of fast activities in the first derivative measurements of the computer-analyzed EEG. Computer EEG (CEEGTM) profiles of LHM showed similarities to those seen after psychostimulant compounds. Methysergide, another analog of LSD-25, produces in quality simi lar computer EEG changes to Lisuride, indicating less potent CNS effects of this compound. Higher dosages of Methysergide could not be given because of side effects. Another anti-migraine compound, Pizotyline, also demonstrated similar CEEG profiles to Methysergide and LHM. The quantitative changes after Pizotyline were also less than those of Lisuride. Cyprohoptadine, a potent antihistamine and antiserotonin, did not show typical "psychostimulant" CEEG profiles. Quantitative pharmaco-EEG (QPEEGTM) studies demonstrated that the "migraine prophylactic" effects of LHM and, in lesser degree, Methysergide may be related to their CNS effects.