The Millon Clinical Multiaxial Inventory (MCMI) has been interpreted as a measure of DSM-III disorders. However, the MCMI was constructed and validated primarily as a measure of Millon's (1969, 1981) taxonomy, not DSM-III. Comparison of the two taxonomies and examination of the MCMI's content validity for two of the MCMI scales indicate only a partial congruence between the Millon and DSM-III taxonomies. There has been no published empirical research concerning the relationship between the MCMI and DSM-III, and the derivation and cross-validation research for the MCMI scales employed Millon's taxonomy and not DSM-III. It is suggested that until such data have been presented one should be cautious in one's interpretation of the MCMI as a measure of DSM-III disorders.