Emerging research implicates biased attention to threat in the pathophysiology of anxiety disorders. Recent findings demonstrate significant associations between attention bias and stress vulnerability. This work has motivated the development of a novel therapy, attention-bias-modification treatment (ABMT). ABMT is designed to implicitly modify patients' biased threat attendance via computerized training protocols. Emerging evidence indicates that ABMT is effective in modifying threat-related attention biases and in ameliorating anxiety symptoms. However, it is unclear whether ABMT is efficacious for Posttraumatic stress disorder (PTSD). The present pilot study is a double blind trial that seeks to examine feasibility, acceptability, safety, efficacy, and risk/benefit ratio of ABMT in individuals with PTSD. In addition this pilot study seeks to identify specific genes associated with anxiety disorders and to examine whether these can predict the success of the ABMT.