Background. Little prospective, multiinstitutional data exist regarding the morbidity and mortality after major pulmonary resections for lung cancer or whether a mediastinal lymph node dissection increases morbidity and mortality. Methods. Prospectively collected 30-day postoperative data was analyzed from 1,111 patients undergoing pulmonary resection who were enrolled from July 1999 to February 2004 in a randomized trial comparing lymph node sampling versus mediastinal lymph node dissection for early stage lung cancer. Results. Of the 1,111 patients randomized, 1,023 were included in the analysis. Median age was 68 years (range, 23 to 89 years); 52% were men. Lobectomy was performed in 766 (75%) and pneumonectomy in 42 (4%). Pathologic stage was IA in 424 (42%), IB in 418 (41%), IIA in 37 (4%), IIB in 97 (9%), and III in 45 (5%). Lymph node sampling was performed in 498 patients and lymph node dissection in 525. Operative mortality was 2.0% (10 of 498) for lymph node sampling and 0.76% (4 of 525) for lymph node dissection. Complications occurred in 38% of patients in each group. Lymph node dissection had a longer median operative time and greater total chest tube drainage (15 minutes, 121 mL, respectively). There was no difference in the median hospitalization, which was 6 days in each group (p = 0.404). Conclusions. Complete mediastinal lymphadenectomy adds little morbidity to a pulmonary resection for lung cancer. These data from a current, multiinstitutional cohort of patients who underwent a major pulmonary resection constitute a new baseline with which to compare results in the future.