The present report is based on an investigation by Kalinowsky and Putnam1 which revealed that diphenylhydantoin sodium is capable of producing distinct changes in behavior in nonepileptic psychotic patients. In view of the observations of Blair, Bailey and McGregor2 and of McEachern,3 who found that this drug could transform querulous, moody and irritable epileptic patients into pleasant, agreeable and congenial persons, it seemed appropriate to study the effect of diphenylhydantoin on certain mental symptoms of other origin. Kalinowsky and Putnam selected 60 patients representing chiefly cases of schizophrenia and manic-depressive psychosis. The duration of the treatment was from two to five weeks, during which time all other therapeutic methods, including psychotherapy, were purposely omitted, so that the effects of diphenylhydantoin could be accurately observed. The initial daily dose was usually 3 to 4 capsules of diphenylhydantoin sodium, 0.1 Gm. (1½ grains) each. After two days the dose