Post-traumatic stress disorder (PTSD) is a chronic and debilitating disorder that affects millions of people each year (Kessler, Chiu, Demler & Walter, 2005). Although effective psychosocial and pharmacological treatments exist for this disorder, estimated non-response rates as high as 50% point to the need for development and evaluation of novel interventions (Schottenbauer, Glass, Arnkoff, Tendick, & Gray, 2008). Biological and cognitive mechanisms associated with re-experiencing symptoms may be directly implicated in the development and maintenance of PTSD (McFarlane, Yehuda, & Clark, 2002). Recent cognitive models and empirical data suggest that diminished ability to control proactive interference, may account for the persistent recurrence of re-experiencing symptoms for some individuals (e.g., Wessel, Overwijk, Verwoerd, & de Vrieze, 2008). The present study tested a novel PTSD treatment approach designed to modify cognitive mechanisms theoretically implicated in the development and maintenance of the disorder. Thirty seven women with PTSD were randomly assigned to an 8-session computerized cognitive training (high interference control requirements) or a control condition (low interference control requirements). Primary dependent outcomes included PTSD re-experiencing symptom severity assessed using the Clinician Administered PTSD Scale and proactive interference control performance assessed using an Operation Span task. Secondary measures included self- reported anxiety and depression as well as cognitive generalization to an alternate task of proactive interference control (CVLT interference index) and a thought suppression task. Results indicated that in both groups PTSD re-experiencing symptoms and Operation Span performance improved, with a larger effect size in the cognitive training group. General distress symptoms also improved over time in both groups. However, CVLT performance and thought suppression ability did not improve from pre- to post assessment. Collectively, results suggest that cognitive training of this type may hold promise as a novel intervention for reducing PTSD symptoms. However, the mechanism of action and implications for models of inhibitory control in PTSD require future study