A study was made of cases observed on a neuropsychiatric service in a rear installation of the Army in the South West Pacific Area.The psychoses were of greatest importance from the point of view of permanent loss of manpower. The possibility that environmental conditions peculiar to the area played an etiologic rôle was discussed. Atypical pictures were common. The impression was obtained that some of the acute cases might be essentially severe emotional reactions brought on by intense stress, perhaps representing "war psychoses" analogous to the acute war neuroses.Among the psychoneuroses, anxiety states occurred with greatest frequency. In the acute conditions the stresses associated with combat played the most important etiologic rôle. In the more chronic cases previous neurotic tendencies were significant factors. Conscious attitudes and problems of morale influenced the picture in a considerable number of cases. Of the whole neurotic group, 69.1 percent of the patients were returned to duty.Measures which might lessen the frequency of psychoneuroses and psychoses in the Army were discussed.Brief mention was made of less common psychiatric conditions and neurologic disorders.