In a previous investigation it was found that the incidence of schizophrenia in a group of 627 British N.C.Os. was much lower than in the average O.R. admissions to hospital. Two questions at once arose: Why was the incidence of schizophrenia low? and How does the disease incidence of British N.C.O. psychiatric casualties compare with other groups admitted to this Base Psychiatric Hospital? The answer to the first may become apparent when we have found the answer to the second.