The conditions of warfare in the present war have so far differed markedly from those in the 1914-1918 war. Up to date (September, 1940) the incidence of psychoses and neuroses appears to be comparatively small. One cannot however foretell what may occur later, and perhaps the following observations on psychoses in officers in the last war may be of some value. They were the subject of a paper I read to the East Sussex Medico-Chirurgical Society in 1920. I have made practically no alterations in the text.