The Millon Clinical Multiaxial Inventory III (“MCMI-III”™) is a popular assessment tool used by clinical psychologists, that has been in use since approximately 1977. This instrument has been the subject of many articles and books.
The theoretical basis derives from Millon’s theory of personality development, personality types, and personality disorders. The instrument relies on 175 “self-report” true false questions, which are dependent upon a subject’s self awareness and providing accurate responses to the questions. 
Similar to other testing instruments the Millon attempts to build in validity scales to account for any misrepresentation of symptoms and attempts to “detect” "invalid profiles.”
The MCMI-III Manual itself specifically acknowledges “limitations and qualifications” regarding its use. The data derives from clinical sampling and “are applicable only to individuals who evidence problematic emotional and interpersonal symptoms or who are undergoing professional psychotherapy or a psycho diagnostic evaluation” and “the samples employed for such purposes are best drawn only from comparable clinical populations.” (T. Millon, R. Davis, P. Millon, , MCMI-III Manual, 2nd
ed. (1997), at p. 6.
It “is not a general personality instrument to be used with normal populations or for purposes other than diagnostic screening or clinical assessment.”
Similar to the MMPI-2, the MCMI-III results may generate computer generated report, the manual itself cautions that “reading a computerized report is no substitute for clinical judgment. Only those trained in the limits of psychological tests are qualified to interpret them."