Systemic tumor embolization during pulmonary resection for lung neoplasms is an uncommon but potentially catastrophic complication. In recent months, two patients undergoing pulmonary resection for bronchogenic carcinoma were found at operation to have tumor extending into a pulmonary vein. Both patients had systemic tumor embolization, one with a fatal outcome because of occlusion of the superior mesenteric artery. The possibility of systemic tumor embolization should be considered in patients with large, central tumors and particularly those that abut the pulmonary veins. The implications of such pulmonary vein involvement is reviewed, and an algorithm for postoperative evaluation and management of these patients is presented.