THE EXTENSIVE USE of phenothiazine drugs in the treatment of emotional disorders and their usefulness in such areas as anesthesiology, obstetrics, geriatrics, and neurology make a knowledge of their side effects, and the treatment of these, important. The most common side effects are of a neurological nature, namely, extrapyramidal effects. An incidence of almost 40% of such drug-induced reactions was reported in a series of several thousand patients being treated with phenothiazines for emotional disturbances. Some of the factors which may play a role relative to this sensitivity are gradually being outlined. Numerous clinical investigations have demonstrated that the drug-induced extrapyramidal-like syndromes are only different from those clinically seen following naturally occurring diseases, such as paralysis agitans ( parkinsonism ) and postencephalitic varieties of basal ganglia disturbances, in that the drug-induced reactions are generally considerd reversible and respond readily to treatment with antiparkinsonian drugs. The recognition and the careful evaluation