OBJECTIVE To investigate the effects of supervised aerobic exercise (AE) and a combined program of supervised aerobic, muscle strengthening, and flexibility exercises (combined exercise [CE]) on important health outcomes in women with fibromyalgia syndrome (FMS). METHODS Randomized controlled trial. METHODS Community-based supervised intervention. METHODS Women (N=64) with a diagnosis of FMS according to the American College of Rheumatology criteria. METHODS Participants were randomly allocated to 1 of 3 groups: supervised AE, supervised CE, or usual-care control. Exercise sessions were performed twice weekly (45-60min/session) for 24 weeks. METHODS The primary outcome measure was the Fibromyalgia Impact Questionnaire (FIQ). Exploratory outcome measures were the 36-Item Short-Form Health Survey, Beck Depression Inventory (BDI), aerobic capacity (6-minute walk test), hand-grip strength, and range of motion in the shoulders and hips. RESULTS Compliance with both interventions was excellent, with women in the exercise groups attending more than 85% of sessions. A 14% to 15% improvement from baseline in total FIQ score was observed in the exercise groups (P≤.02) and was accompanied by decreases in BDI scores of 8.5 (P<.001) and 6.4 (P<.001) points in the AE and CE groups, respectively. Relative to nonexercising controls, CE evoked improvements in the SF-36 Physical Functioning (P=.003) and Bodily Pain (P=.003) domains and was more effective than AE for evoking improvements in the Vitality (P=.002) and Mental Health (P=.04) domains. Greater improvements also were observed in shoulder/hip range of motion and handgrip strength in the CE group. CONCLUSIONS Given the equivalent time commitment required for AE and CE, our results suggest that women with FMS can gain additional health benefits by engaging in a similar volume of CE.