Objective: to apply the McGill Questionnaire, translated and adapted to Brazil, and to identify the degree of internal association between this clinical group of women with fibromyalgia and another group of women with low back pain. Methods: this experimental research includes a case-control study. The population consisted of 83 patients diagnosed with fibromyalgia and low back pain who attended the Orthopedics and Trauma Outpatient Clinic at a Teaching Hospital in Fortaleza-CE, Brazil, from December 2005 to June 2006. The following exclusion criteria were adopted: patients with sensory and cognitive deficits, illiterate, younger than 21 and older than 60 years. A sample of 50 patients was obtained. The control and experimental groups were paired and the MPQ was applied to both. This study has been approved by the Research Ethics Committee of the Federal University of Ceará (04545014-5). Results: were analyzed comparatively through non-parametrical statistics (Kruskal-Wallis). This test found significant means and standard deviations for the sensory and affective categories, with significant p-values for the descriptor “tiring”. Conclusion: the MPQ showed its appropriateness for pain assessment and analysis in fibromyalgia patients. Descriptors: pain; pain measurement; fibromyalgia.