Veterans with Posttraumatic Stress Disorder (PTSD) will be randomly assigned to either Attention Bias Modification Treatment (ABMT) designed to reduce bias toward threat or a placebo control condition not designed to change attention patterns. Outcome measures will be PTSD, anxiety, depression, and alexithymia symptoms as measured by standard psychological interviews and questionnaires. Participants will also be invited to participate in physiological testing before and after receiving AMBT or placebo to serve as additional outcome measures and assess brain functioning, heart rate, and muscle tension.