The clinical results of prefrontal lobotomy were studied in 100 cases of schizophrenia. Ten patients were much improved, 32 were improved, 42 were slightly improved, 14 were unimproved, and 2 were worse. While the figures were more favorable in cases of less than 5 years' duration, worth-while improvement was obtained with considerable frequency in patients who had been ill for periods up to, and even beyond, 20 years.In order to determine what the foregoing results mean in terms of individual mental functions, various symptoms were studied before and after lobotomy. According to these observations, lobotomy leads to amelioration of some of the secondary or less important symptoms; it renders the patients more susceptible to external stimuli, so that they are less able to isolate themselves from the environment; and it reduces certain active reactions to more passive ones, thereby making the patients more tractible. However, prefrontal lobotomy apparently fails to produce any noteworthy improvement of the psychopathologic disturbances which are most important in schizophrenic disorders.In view of these observations the opinion is expressed that the selection of schizophrenic cases for treatment by lobotomy should be confined largely to patients who have been ill for 4 or 5 years or longer.Abstract Teaser