Side effects of phenothiazine tranquilizrs in 10 patients: prochlorperazine in 5 cases, perphenazine in 4 cases, and chlorpromazine and prochlorperazine in one case, are reported. The ages were between 4 and 30 years. The symptoms included occulogyric crisis, opisthotonus, deviation of the lower jaw, torticolis, protrusion of the tongue, trismus, drooling, tremor, carpopedal spasm and dislocation of the mandibular joints. These symptoms were easily controled by the use of relatively large doses of barbiturates or by diphenhydramine injection. The occurence of side effects seems to be related to the mount of accumulated phenothiazines. No sequele was noted in this series of cases or reported in the literature. The awareness of the side effects of these phenothiazines is important in the differential diagnosis of diseases with extra-pyramidal symptomes.