Tai Chi and Aerobic Exercise for Fibromyalgia (FMEx)

Inclusion Criteria: * Age 21 years or older. * Fulfills the American College of Rheumatology (ACR) 1990 classification criteria for FM: (1) a history of widespread musculoskeletal pain on the right and left sides of the body as well as above and below the waist for a minimum duration of 3 months, and (2) pain in 11 or more of 18 specific tender points with moderate or greater tenderness reported upon digital palpation.27 * Fulfills the ACR 2010 diagnostic criteria for FM: (WPI ≥7 AND SS ≥5) OR (WPI 3-6 AND SS ≥9) and does not have a disorder that would otherwise explain the pain28 * Willing to complete the 12-week or 24-week study, including once or twice-a-week exercise sessions. * Willing to abstain from Tai Chi or other new formalized exercise programs until completion of the study if randomized to the Aerobic Exercise. * Willing to abstain from Aerobic Exercise or other new formalized exercise programs until completion of the study if randomized to Tai Chi Exclusion Criteria: * Prior experience with Tai Chi or other similar types of Complementary and Alternative Medicine in the past 1 year such as Qi gong and yoga since these share some of the principles of Tai Chi. * Dementia, neurological disease, cancer, cardiovascular disease, pulmonary disease, metabolic disease, renal disease, liver disease, or other serious medical conditions limiting ability to participate in the Tai Chi or Aerobic Exercise programs, as determined by the study physicians. * Any other diagnosed medical condition known to contribute to FM symptomatology that is not under adequate control for the study period such as thyroid disease, inflammatory arthritis, systemic lupus erythematosus, rheumatoid arthritis, myositis, vasculitis or Sjogren's syndrome. * Inability to pass the Mini-Mental Status examination (with a score below 24) 29 * Enrollment in any other clinical trial within the last 30 days * Plan to permanently relocate from the region during the trial period * Positive urine pregnancy test at baseline or planning pregnancy within the study period * Not English-Speaking: English is the only language to be used during the exercise training program. Our self-reported outcome measures are obtained from validated English-version questionnaires. In addition, using other languages would likely require separate classes, recruitment and instructors which are beyond our current study scope