The MMPI is widely accepted as the best of the questionnaire-type personality tests. It is simple to administer and score, conservative of the clinician's time, well accepted by patients, and provides an extensive anamnesis and a graphic indication of psychopathological status that is easy to interpret. It Should not be used as a substitute for the physician's history-taking (which is so important in the early development of a therapeutic relationship), nor should it be used alone to "make" a diagnosis. With experience in the use of the MMPI, characteristic profiles can be recognized as indicative of personality structure and disturbance that are not limited to diagnostic categories of any particular school. Examples have been selected to demonstrate how the MMPI can be used in measurement of changing psychopathology, thus indicating its value in analysis of clinical progress and results of treatment.