This three-part study examined the reliability and validity of the civilian version of the Mississippi Scale for Combat-Related PTSD using data from the nonveteran participants in the National Vietnam Veterans Readjustment Study. The Civilian Mississippi Scale had a raw score distribution that was roughly symmetric, with an acceptable degree of dispersion and a reasonably high internal consistency reliability coefficient. Overall, however, measurement precision was weaker than that for the military version of the instrument, and confirmatory factor analytic findings differed from those found for the military version. Preliminary investigations of validity were in the form of correlations with indices of stressful life events, a PTSD symptom count, and measures of demoralization and active expression of hostility. The Civilian Mississippi Scale emerged from the various analyses as a PTSD measure with potential but requiring further validational study and perhaps some refinement.