This study was designed to assess whether preoperative trigger-site confirmation using botulinum toxin type A injections significantly improved migraine surgery outcomes. The medical charts of 335 migraine surgery patients were reviewed. Patients who received stepwise diagnostic botulinum toxin type A injections were placed in the botulinum toxin type A group (n = 245). Patients who did not receive botulinum toxin type A or received only therapeutic botulinum toxin type A were placed in the control group (n = 90). The preoperative and 12-month postoperative migraine headache frequency, duration, and intensity were compared to determine the success of the operations. Seventy-two of 90 control patients (80 percent) experienced a significant improvement (a decrease of at least 50 percent in migraine headache frequency, duration, or intensity) at 12 months after surgery, with 29 (32 percent) reporting complete elimination. Of the 245 botulinum toxin type A patients, 207 (84 percent) experienced a significant improvement, with 89 (36 percent) experiencing complete elimination. The surgical success rate of the botulinum toxin type A group was not significantly higher than that of the control group (p = 0.33). Confirmation of trigger sites using botulinum toxin type A does not significantly improve the outcome of migraine surgery. Although botulinum toxin type A can be a useful diagnostic tool, this study demonstrates that there is no statistically significant difference between the injection of botulinum toxin type A and the use of a constellation of symptoms to identify trigger sites. Therapeutic, III.