 While most soldiers exposed to the stresses of the war-zone exhibit psychological resilience, about one-fifth become psychological casualties of war. The fact that such a significant number of soldiers have difficulty adapting to life after war exposure suggests that we need to have well-defined treatments that are effective and cost-efficient. Currently, recommendations for first-line pharmacological management of Post-Traumatic Stress Disorder focus on the use of selective serotonin re-uptake inhibitors SSRIs such as fluoxetine. Despite this recommendation by the DoDVA Clinical Practice Guidelines, there have not been any studies evaluating the effectiveness of these medications in patients that have recently been exposure to war-zone stressors. In fact, studies in Vietnam Era veterans have shown limited effectiveness of SSRIs for PTSD. In addition, there is very limited information available to understand the factors that influence whether a particular soldier will respond to treatment with an SSRI. This study is designed to determine whether fluoxetine is an effective treatment for PTSD and associated conditions in soldiers with recent war-zone exposure, as well as determine whether response to SSRIs is related to the severity of the trauma exposure and PTSD symptoms, psychological resilience, adequacy of social supports family, extra-military and military, post-deployment stressors and life adversity, or the degree of any cognitive impairment. 