The Defence Mechanism Test, the DMT (Kragh, 1969), is claimed to measure defence mechanisms and to reveal important and forgotten experiences in a subject's life. The nature of the responses to this test and the results achieved with it are examined in the light of the psychoanalytic definitions of the defence mechanisms. It is argued that although the responses resemble Freudian defences there is no strong evidence for their validity. Similarly it is shown that the purported parallelism between psychobiography and test responses must be treated with caution. Despite these interpretative caveats the evidence supports the claim that the DMT is a useful test in the clinical setting.