Objective:To detect the expression and distribution of aquaporin1(AQP1) in adenocarcinoma of the lung and to analyze its clinical significance. Methods:The lung tissue of 30 cases of pulmonary adenocarcinoma and 30 normal cases were sampled immediately after surgery to study the expression and distribution of aquaporin1 in adenocarcinoma of the lung by immunohistochemical and Western blot analysis. Results:The sporadic expression of AQP1 was found in the vascular endothelial cells of normal lung tissues. The majority of AQP1 expression could be detected in the vascular endothelial cells,tumor cells in adenocarcinoma of the lung;the expression of AQP1 protein in tumor tissues was remarkably higher than that in normal tissues beside tumors;the expression of AQP1 protein in tumor tissues was correlated with tumor grading and lymph node metastasis. Conclusion:The expression of AQP1 was increased in adenocarcinoma of the lung over normal lung tissues. It suggested that AQP1 might play an important role in the formation and development of adenocarcinoma of lung and the mechanism need to be further studied.