We reviewed 649 primary lung cancer patients with special reference to the occurrence of thromboembolism. Thirteen episodes of thromboembolism were detected in 12 (1.8%) of the 649. Eight of the 12 were men, and their mean age was 63. Adenocarcinoma was the predominant cell type. Most patients had an advanced stage of the disease, but in some in the cancer was at an early stage. In 5 cases, the finding of thromboembolisms led to diagnosis of the lung cancer (38.5%). Anticoagulant therapy was performed in 9 cases, of which 8 responded without serious complication. We emphasize the importance of anticoagulant therapy as a therapy indicated for thromboembolism in patients with lung cancer.