Abstract: Objective To investigate the role of angiopoietin-2 （Ang-2） in control of malignant pleural effusions （MPE） and prognosis in patients with primary lung adenocarcinoma. Methods Using enzyme-linked immunoadsorbentassay， the levels of Ang-2 were measured in both pleural effusions （PE） and serum from a total of 79 lung adenocarcinoma patients with MPE. Data was analyzed with the efficacy of MPE control and prognosis. ResultsThe level of Ang-2 in PE was （26.67±8.82）pg／ml， and （361.18±97.58）pg／ml in serum. Ang-2 level in PE was the only one significant factor for MPE control when comparing with other demographic and laboratory data. Ang-2≥25.57 pg／ml in PE was used as a cut-off point for failure control of MPE. Logistic regression analysis showed that the level of Ang-2 in PE was an independent factor in the local control of PE（OR=5.65，95%CI：2.40-16.78，P<0.001）. In a multivariate analysis， the level of Ang-2 in PE （HR=1.15，95%CI：1.01-1.32） and MPE control status （HR=0.42， 95%CI：0.19-0.89） were confirmed as independent prognostic factors for overall survival. Conclusion The level of Ang-2 in PE appears to be a reliable surrogate marker in evaluating the therapeutic efficacy in the control of MPE and prognosis.