Journal of Traumatic Stress, Vol. 13, No. 1, 2000 Dimensionality and Reliability of the Civilian Mississippi Scale for PTSD in a Postearthquake Community Moira Inkelas, 1 Laurie A. Loux, 2 Linda B. Bourque, 3,5 Mel Widawski, 4 and Loc H. Nguyen 3 This study examines psychometric properties of the Civilian Mississippi Scale for posttraumatic stress disorder when administered in a community survey of 656 per- sons following the 1989 Loma Prieta earthquake. Internal consistency was lower (Cronbach’s α = .73) than for previous analyses of civilian and combat versions of the Mississippi Scale. The analysis produced one strong factor composed of 25 items with regular wording and a second, weaker factor composed of 10 items with reversed wording. Internal consistency was higher when the 10 reversed items were removed (Cronbach’s α = .86); the two factors were negatively correlated. Traumatic experiences and psychological distress measures explained more vari- ance in the 25-item factor than in the 35-item scale. Further studies should focus on content analysis and performance of the reversed items. KEY WORDS: PTSD; Mississippi Scale; disaster; community survey; reliability; validity; assessment. The Mississippi Scale for Combat-Related Posttraumatic Stress Disorder (Keane, Wolfe, & Taylor, 1987) has been shown to be a reliable, valid, and easily administered screening measure for PTSD among military veterans, particularly those who saw conflict during the Vietnam War (Kulka et al., 1990, 1991; McFall, Smith, Mackay, & Tarver, 1990). The Mississippi Scale has been adapted for use 1 RAND Corporation, Santa Monica, California. 2 University of Michigan, Ann Arbor, Michigan. 3 Center for Public Health and Disaster Relief and Department of Community Health Sciences, School of Public Health, University of California, Los Angeles, California. 4 Office of Academic Computing, University of California, Los Angeles, California. 5 To whom correspondence should be addressed at Center for Public Health and Disaster Relief and Department of Community Health Sciences, School of Public Health, University of California, Box 951772, Los Angeles, California 90095-1772. Fax: (310) 794-1805. 149 0894-9867/00/0100-0149$18.00/1 C  2000 International Society for Traumatic Stress Studies