The Purdue Post-traumatic Stress Disorder Scale is a 15-item self-report instrument based on the DSM-III diagnostic criteria for post-traumatic stress disorder. This scale is a quick easily administered, measure of psychological reactions to a traumatic event. The goal of the present report is to validate this instrument for use as a measure of long-lasting combat stress reactions of American Vietnam veterans. The PPS demonstrated a high degree of internal consistency with a Cronbach's coefficient alpha of 0.94. The PPS demonstrated construct validity through significant correlations with other self-report measures of combat experience and residual psychological distress, and through a factor analysis yielding three factors, labeled as arousal, avoidance, and the global perception of distress. Results support further use of the Purdue Post-traumatic Stress Scale as a research instrument for assessing the long-term impact of a traumatic event.