To treat bilateral pulmonary metastases during a single operation, simultaneous bilateral thoracotomy via median sternotomy is usually employed. With this approach, however, it is sometimes difficult to access lesions located on the dorsal side of the left lower lobe. We have explored the use of clamshell incisions for such difficult cases. From 1990 to 1995, we studied the use of clamshell incisions in 14 patients with bilateral pulmonary metastases. The average duration of surgery was 212 minutes, the average volume of intraoperative blood loss was 477 ml, and the average number of metastatic lesions extirpated was 23. The endotracheal tube could be removed immediately after the operation in 12 patients, while the remaining 2 patients, who underwent an extensive operation, needed 3 and 4 days of intubation. The arterial blood gas analysis on the first postoperative day for the former 12 patients was as follows: the average value of PaCO2 was 44.4 mmHg, and the average value of PaO2 was 140.4 mmHg (FiO2 = 0.4). None of the patients experienced severe pain or respiratory distress that impaired their daily activities due to continuous epidural anesthesia following surgery. The length of time from surgery to discharge was relatively short, averaging 22 days. We have not encountered any sternal override in our patients. Although we cannot ignore the biological behaviour of primary tumors when selecting a surgical approach, the clamshell incision seems to provide a useful means of thoracotomy when treating bilateral pulmonary metastases. We intend to use this approach in future, taking into careful consideration the indication of each individual case.