DESCRIPTION (provided by applicant): Posttraumatic Stress Disorder (PTSD) is debilitating and common (up to 30% in Vietnam Veterans and 16% in Afghanistan and Iraq Veterans). A significant number of Veterans do not engage in or drop-out from effective trauma-focused therapies due to avoidance from trauma-related memories. Because of this limitation, and because scientific literature suggested that acupuncture might be effective for PTSD symptoms, we developed an acupuncture intervention for PTSD and conducted a clinical trial that showed positive effects. This remains the only high quality trial of acupuncture for PSTD published, because of which the current VA/DoD guidelines for PTSD state that acupuncture is a "B" recommendation (fair evidence, provide service) for PTSD treatment. That civilian study compared acupuncture to an effective therapy (CBT) and a wait-list control, but did not have a placebo control. And, research has shown that Veterans may respond differently to therapies than civilians. More definitive data about the efficacy of acupuncture for PTSD is required in order to recommend it as an "A" evidence-based intervention for PTSD in Veterans. Specifically, it is important to show that acupuncture is better than a placebo control and that it has effects on biological abnormalities of PTSD. The aim of this study is to demonstrate efficacy of acupuncture for PTSD by showing clinical and biological effects that are statistically larger and clinically more important than effects of "sham" acupuncture. Given current knowledge and the need for efficient, ethical and best practices within an experimental design, the primary aim is best accomplished by a randomized controlled trial comparing verum acupuncture (ACU) to placebo minimal needling sham acupuncture (MIN). The goal is to evaluate ACU for a significant positive signal, not to compare ACU to other interventions or to evaluate treatment durability. Acupuncture is delivered in 24 sessions over 12 weeks. The primary hypothesis is that efficacy of ACU for PTSD symptom severity will be large (pre- to post- treatment Cohen's d > 0.8), and significantly better than MIN (between group Cohen's d > 0.30, with 80% probability of detecting a true group difference at p<0.05 (2-sided). The secondary hypothesis is that compared to MIN, ACU will be associated with a significantly larger change from pre- to post-treatment in psychophysiological response (decreased startle by EMG eye blink during fear conditioning procedure). The study design is a two-arm, parallel-group, prospective RCT. The sample frame is Veterans with chronic PTSD with a sample of convenience from those seeking care at the Long Beach VA. Exclusion criteria are meant to keep out individuals with characteristics that are known to be PTSD treatment confounds, associated with non- adherence or negative response to treatment, that may significantly affect biological assessment, or who may be put at risk of harm. The samp...