Background: Thoracotomy is associated with significant pain and morbidity. Methods: We performed a prospective randomized trial over 4 months. Patients were randomized to a standard posterior-lateral thoracotomy or an identical procedure, except an intercostal muscle was harvested from the lower rib (to protect the intercostal nerve) before chest retraction. To ensure an equal distribution among both groups, patients were stratified by race, sex, and type of pulmonary resection. All patients received similar pain management. Pain was assessed by using multiple pain scores during hospitalization and after discharge. Outcomes assessed were pain scores, spirometric values, analgesic use, and activity level. Results: There were 114 patients. The median time for intercostal muscle harvesting was 3.7 minutes. The numeric pain scores were lower for the intercostal muscle group on postoperative days 1 and 2 and at weeks 1, 2, 3, 4, 8, and 12 (P < .05 for all). In addition, patients in the intercostal muscle group had a smaller decrease in spirometric values, were less likely to be using analgesics, and were more likely to have returned to normal activity. Conclusions: The harvesting of an intercostal muscle flap before chest retraction decreases the pain of thoracotomy and leads to a lower decrease in spirometry. In addition, patients have less pain at 1, 2, 3, 4, 8, and 12 weeks postoperatively and are less likely to be using narcotics. Finally, it offers a pedicled muscle flap that takes little time to harvest and is able to buttress all bronchi after lobectomy. Copyright © 2005 by The American Association for Thoracic Surgery.