As a Psychiatrist working at Veterans Affairs Hospital, I have seen many patients with co existence of Obstructive Sleep Apnea and PTSD. As we know sleep disturbances are very common in combat veterans with PTSD, most common of which are nightmares and insomnia. There have been studies showing that people with OSA can have worsening of PTSD but PTSD is not found to be deleterious for OSA. CPAP is the treatment of choice for OSA and it has been found that people who start using CPAP machine have less occurance of nightmares and they sleep better. There is considerable ratio of veterans seen in my practice who do not use CPAP despite being prescribed for it, I compared the veterans with OSA who use CPAP mahcine versus those who do not use CPAP machine. Patient's subjective reporting of improvement in PTSD symptoms in those who use CPAP machine will be compared to those who do not use CPAP machine and continued to have PTSD symptoms.