Metastasis of lung cancer to the digestive tract (excluding the esophagus) was confirmed by surgery or autopsy in 30 of the 1635 lung-cancer patients admitted to this Center during the 17-year period since 1977. The diagnosis was made before death in 7 and after death in 23. Metastasis of large cell carcinoma was the most common (3.7%), followed by adenocarcinoma (2.4%), small cell carcinoma (1.7%), and squamous cell carcinoma (0.7%). Metastasis to the stomach occurred in 0.4%, to the small intestine in 1.1% and to the colon in 0.5%. The overall percentage of metastasis to the digestive tract was 1.8%. Among the 298 cases diagnosed at autopsy, metastasis to the digestive tract occurred in 9.7%; stomach, 2.6%; small intestine, 5.7%; and colon, 3.0%. Eleven of the patients in whom the diagnosis was made at autopsy had abdominal symptoms while they were alive. In 11 cases diagnosed at autopsy, occult blood was positive in 9, but 6 of those 9 patients were asymptomatic. The occult-blood test is considered to be helpful as a supplementary diagnostic method in detecting metastasis of lung cancer to the digestive tract. Among the cases diagnosed while the patients were alive, metastasis was observed in the small intestine in 6 and in the colon in 1. The major manifestations were melena, ileus, intussusception, and perforation; 4 patients required emergency surgery. The prognosis was poor: the mean survival period from the onset of symptoms was 49 days. The direct cause of death was metastasis to the digestive tract in 5 cases. The possibility of metastasis to the digestive tract is high when progressive abdominal symptoms are observed and the stool is persistently positive on occult-blood tests.