Objective. To identify predictors of maintenance of exercise for women with fibromyalgia (FM).Methods. Women with FM who had been randomized to the exercise arm of a clinical trial were studied prospectively during and 3 months following treatment. Subjects completed exercise logs weekly and returned the data via postal mail. Outcome variables were duration of aerobic and stretching exercises. Two separate multivariate models for longitudinal data were built with adjustment for in-treatment adherence and time. Pretreatment characteristics (self efficacy, pain, disability, stress, exercise barriers and benefits, and age) and changes during treatment (pain, disability, stress, and exercise barriers and benefits) were considered potential predictors of exercise maintenance. Results. Stretching significantly decreased in the 3 months following treatment. High stress at baseline and increases in stress during treatment were associated with poor maintenance of stretching. Disability at baseline (measured with the Fibromyalgia Impact Questionnaire), an increase in barriers to exercise during treatment, and increases in upper-body pain during treatment were associated with worse maintenance of aerobic exercise in the 3 months following treatment. Conclusion. The maintenance of an exercise program in women with FM appears to be contingent on being able to deal with stress, pain, barriers to exercise, and disability.