The objective of the present study was to evaluate instruments used to assess pain in patients with fibromyalgia (FMS). Participants were 602 patients with FMS. Pain was measured with five scales: a visual analog scale (VAS), the Pain Rating, Present Pain, and Number of Words Chosen Indexes from the McGill Pain Questionnaire; and intensity of pain obtained from a manual tender point exam. The VAS had the highest correlations with other measures of pain and with self-efficacy for pain, physical functioning, fatigue, and stiffness. The correlations between the VAS and fatigue and stiffness were significantly higher than those of other pain measures (p < .01). Our findings suggest that the easy-to-administer VAS may be the most useful measure of pain with patients with FMS.