We hypothesized that fibromyalgia (FM) patients would report lower levels of psychological control mechanisms and that higher levels of control would moderate key symptoms associated with FM, such as pain, fatigue, perceived stress, and mood disturbance. METHODS: Ninety-eight women with FM diagnosed according to American College of Rheumatology criteria and 35 matched pain-free women were identified. Applied questionnaires included the Fibromyalgia Impact Questionnaire, Profile of Mood States, Perceived Control of Internal States Scale, Perceived Stress Scale, and Mastery Scale. Differences were sought using t-tests, one-way analysis of variance, bivariate correlations, and multiple regression analysis. RESULTS: Comparison between FM patients and healthy individuals found significant differences in control (Perceived Control of Internal States Scale and Mastery Scale), pain, perceived stress, fatigue, confusion, and mood disturbance (all P <0.001). There were significant associations found between both high and low levels of control on stress, mood, pain, and fatigue (P <0.001-0.05). Strong negative correlations were present between internal control and perceived stress (P <0.0005). CONCLUSION: FM patients use significantly different control styles compared with healthy individuals. Levels and type of psychological control buffer mood, stress, fatigue, and pain in FM. Control appears to be an important up-stream process in FM mechanisms and is amenable to intervention.