This paper discusses Minnesota Multiphasic Personality Inventory (MMPI) data obtained from individuals exposed to chlorine dioxide in the workplace who developed Multiple Chemical Sensitivity Syndrome. The paper explores current research on chlorine dioxide exposed persons who were misdiagnosed on the basis of MMPI interpretations. Difficulties may exist in using the MMPI or MMPI-2 in psychological assessment due to potential validity problems. It is recommended that more data be collected to determine if current MMPI data should be updated to reflect newer disease entities involving multiple organ systems. (SR)