Background: In the resection of lung cancer, pneumonectomy occupied $20 {\~}35\%$ of all resections, and significantly high operative mortality is reported in right pneumonectomy ($10{\~}25\%$). The aim of this study is to identify the characteristics of morbidity, operative mortality and factors affecting operative mortality after pneumonectomy. Material and Method: This study recruited the database which performed pneumonectomy for lung cancer in Korea Cancer Center Hospital from Aug 1987 to Apr 2002. Result: Total of 386 pneumonectomies were peformed in that period. Sidedness were left in 238, right in 148; and the procedures were standard resection in 207, and extended resection in 179. Morbidity occurred in 115 cases ($29.8\%$, 115/386). Mortality occurred in 12 cases ($3.1\%$, 12 in 386). This mortality rate was similar to that of lobectomy ($2.1\%$, 13 in 613) during the same period. Morbidity consisted of 42 hoarseness, 17 (9) pneumonia and ARDS, 8 empyema, 5 (1) broncho-pleural fistula, 5 reoperation for bleeding, 5 (1) arrhythmia, 1 (1) pulmonary edema, and 25 others (The number in the parenthesis is the number of mortality case for that morbidity). Several factors affecting the operative mortality were evaluated. At first, extended procedure ($3.3\%$, 6 in 179) affected the operative mortality similar to the standard procedure ($2.9\%$, 6 in 207)(p=0.812). Second, the rate of operative mortality in an elderly group over 60 years ($5.5\%$, 10 in 182) was significantly higher than the younger group under 60 years ($1\%$, 2 in 204)(p=0.016). Third, sidedness of resection affects to operative mortality. Right pneumonectomy ($6.8\%$, 10 in 148) showed higher operative mortality than that of left pneumonectomy ($0.8\%$, 2 in 238)(p=0.002). The group over 60 years showed higher incidence of respiratory morbidity ($11.0\%$, 20 in 182) than that of the group under 60 years ($3.4\%$, 7 in 204)(p=0.005). Right pneumonectomy also showed significantly higher incidence ($11.5\%$, 17 in 148) than that of left pneumonectomy ($4.2\%$, 10 in 238)(p=0.008). Conclusion: Age and sidedness of pneumonectomy were the risk factors of operative mortality and respiratory complications, Therefore, careful selection of patients and more attention perioperatively were demanded in right pneumonectomy. However, because the operative mortality is acceptable, pneumonectomy could be done safely if the pneumonectomy is necessary for curative resection of lung cancer.