The goal of this translational research project is to generate a pilot sample of data from an investigation of a novel therapeutic approach to post traumatic stress disorder (PTSD). Current treatments for PTSD include exposure and other aspects of cognitive therapy as well as drug therapies based on serotonin-reuptake inhibiting antidepressant agents. However, these treatments are often unsuccessful, and symptoms in affected individuals may persist for decades. The central hypothesis guiding this research project posits that acquired fear responses, such as those in PTSD, when reactivated by recall become sensitive to noradrenergic modulation and thus may be permanently attenuated by blocking noradrenergic transmission. Further, we predict that this attenuation will facilitate subsequent therapy. In the current study, we will be investigating this model in three groups of Veterans of either Operation Iraqi Freedom or Operation Enduring Freedom (OIF/OEF) with PTSD: 1) Individuals who receive propranolol following recall of a traumatic memory (Propranolol-trauma); 2) Individuals who receive a placebo following recall of a traumatic memory (Placebo-trauma), and; 3) Individuals who receive propranolol following recall of an affective neutral memory (Propranolol-neutral). In addition, traumatic memory recall will be psychophysiologically assessed by measuring Veterans' facial corrugator electromyography (EMG), skin conductance, blood pressure and cardiovascular inter-beat interval responses pre- and two weeks post-medication administration.