There are conflicting theories as to the cause of German aggressiveness and the appropriate cure. Possibly aggressiveness has become an autonomous habit and will not disappear when the original causes are removed, but the causes should be known before treating cases. The author describes eleven types of aggressors among the Germans, showing differences in the source of aggression and in the role of ideational factors. He considers plans for postwar re-education useless until we know the relative numbers and location of each type. Until after the war, information can only be obtained from aliens and prisoners in this country. (PsycINFO Database Record (c) 2006 APA, all rights reserved)