T he Millon Clinical Multiaxial Inventory (MCMI) was originally created as the Millon Illinois Self-Report Inventory (MISRI) to measure the prototypes of Theodore Millon's (1969) personality theory. Shortly thereafter, the MISRI was expanded to include other diagnostic entities besides personality, and it lost the Illinois part in its title when Millon moved to the University of Miami (Millon, 1977). Millon believed that neither his theory nor his test should remain static, and the current version of the test is in its fourth edition (MCMI-IV;Millon, 2015). This chapter describes the instrument, particularly with regard to the assessment of disordered thinking, review its operating characteristics, and note the questionnaire's advantages and disadvantages. Before I do that, however, I am going to introduce the MCMI by using a fictional character whom you may know.The main protagonist in the film Whiplash (Chazelle, 2014) is Terence Fletcher, portrayed by J. K. Simmons in the film. Fletcher is an abusive, narcissistic jazz instructor. He played mind games at the expense of his students. At one point, for instance, he insisted that a student's instrument was out of tune and dismissed the student, although he later told the group that the instrument was actually not out of tune, and then he faulted the student for not standing his ground. He recruited three different percussionists and repeatedly and abrasively dismissed one and selected another. Eventually, he was fired by his university because of his mistreatment of students. When I teach a course that includes the MCMI-IV, I have my students watch the