1. In a series of 120 cases showing manic-depressive, dementia præcox, psychoneurotic, and psychopathic personality reactions, the removal of focal infection in 58 cases did not result in a higher percentage of improvement or recoveries than in a comparable group of 62 cases in which foci of infection were not removed.2. Reviewing the entire group of operated cases showing recovery or improvement, and comparing the original prognoses with the subsequent course, our observations demonstrate that in every case that recovered, a recovery had been forecast before treatment was started; and that no case recovered in which a poor prognosis had been given. Furthermore, in only one case did an unexpected improvement occur.3. A critical study of the methods used by Cotton for establishing focal infection has proven them to be unsatisfactory for teeth, stomach, lower intestine, and cervix.4. It is desirable to eliminate focal infection when adequately demonstrated in psychotic patients in the same way as one should attempt to alleviate any physical disorder in mentally diseased patients. Nevertheless, it has not been shown that focal infection is the etiological factor in the functional psychoses.