This report summarizes data gathered thus far from an ongoing study. Two groups (total N = 12) of Vietnam War veterans diagnosed with Posttraumatic Stress Disorder (PTSD) received a single session of exposure or Eye Movement Desensitization and Reprocessing (EMDR) focusing on the veterans' most distressing war experience. Group assignment was random, treatment providers were blind to assessment data, and the pre- and posttreatment assessor was blind to treatment assignment. Both groups showed improvement on the Impact of Event Scale. EMDR treatment resulted in greater positive changes in within-session Subjective Units of Discomfort levels and on self-monitored severity of intrusive recollection. A trend toward decreased heart rate reactivity was observed in both groups. Results must be considered carefully due to the small number of subjects used in the study.