Thirty-eight patients in stuporous states or in active psychoses without evident cause showed prompt and often very impressive improvement after treatment with nicotinic acid.The usual criteria for the clinical diagnosis of pellagra or of other deficiency syndromes were absent.This experience leads us to believe that many patients whose psychiatric status suggests the diagnosis of toxic psychosis or exhaustion delirium may be relieved of their symptoms by the administration of nicotinic acid. It is believed that in such cases and in cases who show unexplained clouding of consciousness a therapeutic trial of nicotinic acid is the only means available by which one can determine whether or not the psychosis is due to avitaminosis.In some exceptional cases, even when clinical evidence of pellagra is absent, extremely large amounts of nicotinic acid are necessary to obtain satisfactory results.Abstract Teaser