This preliminary report describes a new brief interview based assessment of post-traumatic stress disorder using an 8-item treatment-outcome post-traumatic stress disorder scale (TOP-8). The TOP-8 was developed from a larger post-traumatic stress disorder evaluation scale based on items which occurred frequently in the population and which responded substantially to treatment across time. The 8 resultant items were drawn from all three symptom clusters for post-traumatic stress disorder, and showed an improved ability to detect drug versus placebo differences in comparison with the original scale. The eight-item treatment-outcome post-traumatic stress disorder scale also correlated significantly with a self-rated measure of post-traumatic stress disorder and distinguished at a highly significant level between responders and non-responders on an independently judged Clinical Global Impressions measure. The results of this study are discussed and future directions suggested.