Objectives: Intracostal suture or intercostal muscle flap can reduce post-thoracotomy pain through the preservation of intercostal nerves below or above the incision. This study aims to test whether combining intracostal suture with intercostal muscle flap might achieve better pain relief than intracostal suture alone. Methods: This study included 144 consecutive patients who underwent pulmonary resection. Eighty patients entered the trial but eight were excluded. Seventy-two patients were randomly assigned to a muscle flap group, in which the fifth intercostal muscle and neurovascular bundle were raised and intracostal suture on the sixth rib was applied. For the control group, only intracostal suturing on the sixth rib was done. All patients had a functional epidural placed, which were removed 24 h after surgery. Differences on average numeric rating scale (aNRS) scores were assessed in an early post-operative period from day 1 to day 7 and a later period from week 2 to week 12, when patients were resting or coughing. The doses of oxycodone demand and hyperalgesia-related intercostal dermatomes (HIDs) were recorded for analysis. Results: No differences were noted between the two groups in terms of length and width of the incision, or duration of rib retraction. Neither in different time periods (early or late) nor the activity status (while resting or coughing) yielded a statistical difference on aNRS scores between the muscle flap group and the control group (muscle flap group vs control group: mean (95% confidence intervals) from d ay 1 to day 7, 4.42 (1.56-7.28) vs 4.79 (2.03-7.55) on coughing (p = 0.282); median (inter-quartile range, IQR) from day 1 to day 7, 1.71 (0.86-3) vs 2.50 (1.16-3.12) while resting (p = 0.279); median (IQR) from week 2 to week 12, 0.43 (0-0.86) vs 0.48 (0.06-1.20) on coughing (p = 0.595); median (IQR) from week 2 to week 12, 0 (0-0.14) vs 0.05 (0-0.14) while resting (p = 0.856)). No differences were found in total oxycodone consumption from day 1 to day 7 between the two groups (Z = -1.821, p = 0.069). The rate of HIDs in each intercostal space and median number of HIDs were similar between the two groups on day 1 (p > 0.05) and day 7 (p > 0.05). Conclusions: The combination of intracostal suture with intercostal muscle flap may not necessarily achieve better post-thoracotomy pain control than using intracostal suture alone. © 2009 European Association for Cardio-Thoracic Surgery.