Over 40,000 Veterans who served in the 1991 Gulf War (GW) have a persistent form of chronic multisymptom illness that defines Gulf War Veterans Illness (GWVI). With no existing proven treatments to provide relief to these sufferers, it is critical to find efficacious and acceptable treatments for GWVI. Our long-term goal is to develop a safe, readily available, mind-body treatment to reduce pain and other chronic symptoms and enhance wellness in Veterans with GWVI. Tai Chi is a traditional Chinese mind-body therapy that has been practiced for centuries. In the last decade, we have demonstrated that Tai Chi can improve both physical health and psychological well-being in patients with a variety of chronic conditions. The proposed randomized trial will establish the effectiveness of a Tai Chi mind-body treatment in Veterans with GWVI. One hundred and twenty participants meeting criteria for GWVI will be randomly assigned to either a Tai Chi exercise or a stretching and wellness education group for 12 weeks with a post-treatment assessment, and follow-up assessments. For an exploratory sub-study, 40 Veterans (approximately 20 from each condition) will undergo MRI scanning at each assessment point. We will accomplish the following Specific Aims: Specific Aim 1: Evaluate whether the Tai Chi intervention will reduce symptoms of pain in Veterans with GWVI more than the Wellness intervention. We hypothesize that participants randomized to the Tai Chi intervention will show a greater reduction in pain symptoms than those in the Wellness intervention and will maintain changes over a 9-month follow-up period. Specific Aim 2: Evaluate whether the Tai Chi intervention improves fatigue, cognition, quality of life, and physical functioning in GW Veterans with GWVI, as compared to the Wellness intervention. We hypothesize that participants randomized to the Tai Chi intervention will evidence more improvement in fatigue, cognitive functioning, quality of life, and physical functioning than those randomized to the Wellness intervention and will maintain changes over a 9-month follow-up period. Specific Aim 3: Explore a potential neurobiological mechanism by which Tai Chi can reduce pain and other symptoms and improve quality of life in Veterans with GWVI. We hypothesize differences in resting state fMRI and on diffusion tensor imaging (DTI) in participants randomized to the Tai Chi intervention compared with Wellness intervention participants and that these differences will maintain over the 9-month follow-up period. The proposed trial, informed by our prior investigations, with a robust study design and strong research team, will produce valuable results that can have a direct and immediate impact on healthcare practices for GWVI. If proven as an effective treatment for the symptoms of GWVI, this non-pharmaceutical treatment could easily be implemented in VA facilities, and Veterans could be taught how to continue to practice independently within their own homes. Providing GW Veterans even moderate relief from chronic and debilitating symptoms of GWVI could have a profound impact on improving their overall sense of well-being and quality of life, the ultimate measure of treatment efficacy.