To develop new Minnesota Multiphasic Personality Inventory (MMPI) scales for diagnosing acute and chronic posttraumatic stress disorder (PTSD), 237 civilians with PTSD or panic disorder (controls) completed the MMPI-R. All 399 items were submitted to chi-square analysis to select those differentiating acute or chronic PTSD from controls. The analyses yielded an MMPI Acute PTSD scale (32 items) and a MMPI Chronic PTSD scale (41 items). Discriminating between acute PTSD and controls, the MMPI Acute PTSD scale had a hit rate of 83% and the MMPI Chronic PTSD scale produced a hit rate of 75% to 80%. Cross-validation produced similar hit rates. These scales scores were not substantially influenced by gender or types of traumatic events, and only the MMPI Acute PTSD scale seemed to not be sensitive to co-morbidity.