At our institute patients with lung cancer had traditionally undergone lobectomy with mediastinal lymph node dissection using a standard posterolateral approach. The considerable morbidity associated with the standard posterolateral thoracotomy led us to investigate an alternative muscle-sparing approach. A prospective, randomized study of 30 patients with primary lung cancer (stage I or II) was performed to compare the following: operative field size, number of dissected lymph nodes, surgery time, postoperative pain, shoulder range of motion, and pulmonary function test results between patients who underwent either standard thoracotomy (SP group, n = 15) or the muscle-sparing thoracotomy (MS group, n = 15). The procedure should provide enough operative field size to access to mediastinum. Compared with the standard posterior thoracotomy, the muscle-sparing thoracotomy supplied a smaller operative field (218 +/- 31 versus 165 +/- 41 cm2) and required more surgery time (87 +/- 13 minutes) than the standard posterior thoracotomy (66 +/- 12 minutes). There were no significant differences in the number of dissected mediastinal lymph nodes. During the early postoperative days, pain and restriction of shoulder flexion were significantly less in the MS group than in the SP group. There were no significant differences in pulmonary function between the two groups. In terms of the operative field there is a marked disadvantage with the muscle-sparing incision compared with standard thoracotomy. The operative field is significantly smaller than with a standard thoracotomy, requiring more time to dissect the mediastinum; however, the pain is less and shoulder range of motion is superior to what is seen after standard thoracotomy during the early postoperative period. We conclude that there is no overall advantage to using the muscle-sparing incision in patients with lung cancer.