Objective: It is appropriate to acknowledge that despite treatment, Post Traumatic Stress Disorder (PTSD) continually debilitates many Vietnam veterans. Although therapies have been developed, remission is hard to obtain with either pharmacotherapy or psychotherapy. Evidence has suggested that some forms of yoga may reduce sympathetic overactivity and increase parasympathetic activity, thereby improving stress resilience. Sudarshan Kriya Yoga (SKY) was hypothesized in this study to be potentially useful for lessening symptom severity on the Clinician Administered PTSD Scale (CAPS) in Vietnam veterans with treatment-resistant PTSD.