Post-traumatic stress disorder (PTSD) is characterized by three symptom groupings: re-experiencing symptoms including flashbacks, nightmares, and intrusive memories; physiological hyperarousal; and avoidance symptoms. Of the three major categories of symptoms in PTSD listed by the Diagnostic and Statistical Manual of Mental Disorders, sleep-related problems are listed in two of them: difficulty falling asleep is considered an aspect of hyperarousal symptoms, and nightmares are a type of re-experiencing symptom. Both are found commonly in PTSD. Little is known about the relationship of neuroendocrine dysregulation in PTSD and sleep disturbance. It is possible that successful treatment of sleep disturbance in PTSD may alter an abnormal stress hormone pattern. The novel cyclopyrrolone hypnotic eszopiclone thus presents an intriguing opportunity to examine the treatment of sleep disturbances and nightmares in PTSD. This study will determine the safety, efficacy and impact on neuroendocrine parameters of eszopiclone compared to placebo for sleep disturbance and overall PTSD symptoms in individuals with PTSD and reported sleep disturbance.