The Defense Mechanism Inventory, a paper and pencil test which purports to measure the relative intensity of usage of five major groups of defenses, is described. The inventory consists of 10 brief stories, two per conflict area, followed by four questions regarding S's actual behavior, fantasy behavior, thoughts, and feelings in the situations described. Five responses typifying the five defenses (i.e., hostility-out, projection, principalization, turning-against-self, and reversal) are provided for each question, from which S selects the one most representative and the one least representative of his reaction. Reliability, validity, and normative studies are presented, all indicating that this inventory has many potential uses as a clinical and research instrument.