We investigated the utility of the newly revised version of the Minnesota Multiphasic Personality Inventory, the MMPI-2, for assessing psychopathology in three diagnostic headache groups: Post Traumatic, Status Migrainosus, and Status Migrainosus with Analgesic Rebound. We also investigated whether distinct clusters of headache sufferers could be identified using the MMPI-2 clinical scales, and whether these clusters coincide with headache diagnosis. Eighty-one patients in treatment at the Houston Headache Clinic were diagnosed and administered the MMPI-2. Significant levels of psychopathology were found in all three diagnostic groups. Furthermore, Cluster Analysis identified three clusters of patients with equal proportions of patients from the three diagnostic groups. Cluster 1 patients were abnormally high on many MMPI-2 clinical scales; Cluster 2 patients showed more moderate elevations, and Cluster 3 patients had essentially normal profiles. We concluded that the MMPI-2 offers additional information not available through medical diagnosis alone. Thus, it is crucial to include psychological assessment in any comprehensive evaluation of chronic headache patients.