Objective:To investigate the clinical characteristics and prognostic factors of primary signet-ring cell adenocarcinoma of lung. Methods:The clinical features of 22 patients with primary signet-ring cell adenocarcinoma of lung from the year 1981 to 2007 were analyzed retrospectively and made a statistical analysis on the prognostic factors. Results:Postoperative pathologic examination was an important method to confirm the primary signet-ring cell adenocarcinoma of lung and surgery was the main therapeutic approach. The 1-, 3-, and 5-year survival rates were 63.0%, 53.3%, and 37.7%, respectively. Statistical analysis indicated that smoking, tumor size, complete resection, and tumor staging were the independent prognostic factors for patients with primary signet-ring adenocarcinoma of lung.Conclusion:The primary signet-ring cell adenocarcinoma of lung has higher malignancy. Invasion and migration frequently occur. Its prognosis is poor.