 Oxytocin OT - a neurohormone and neuromodulator which is mainly synthesized in the hypothalamus - is a mediator stress regulation and improves social bonding. Recently, several theoretical studies suggested that PTSD patients have abnormal functioning of the OT system. According to these theories, dysfunction in the oxytocin system may modulate the interpersonal impairment that characterizes PTSD, and therefore intranasal OT may potentially relieve these symptoms. In two current studies that were conducted in Rambam health care we found that a single dose of intranasal OT reduces anxiety and irritability symptoms, and enhances emotional empathy and compassion, in patients with PTSD. The main goal of this study is to examine the effects of 21-days intranasal Oxytocin on clinical symptoms and social function in these patients. 