Objective To explore the diagnostic values of adenosine deaminase (ADA) activity,C-readive protein (CRP) content and IFN-γ content for tuberculous pleurisy.Methods Fifty-nine cases with tuberettlous pleurisy,20 cases malignant tumor with pleural fluid and 12 cases of the other pleural fluid were studied,ADA activity,CRP content and IFN-γ content of pleurnl fluid and serum were detected in those patients.Results The pleural fluid activity of ADA[(50.98±13.07)U/L],content of CRP[(142.90±51.42)mg/L]and content of IFN-γ [(139.46±70.43)ng/L] in tuberculous pleurisy were significantly higher than those in malignant tumor and the other pleural fluid (P＜0.05 or＜0.01).When regarded 45 U/L as critical value of ADA in tnberculous pleurisy,the sensitive rate,special rate and clinical diagnose accordance rate were 80.4%,96.9%and 86.4%respectively,110,mg/L as critical value of CRP,they were 78.6%,81.2%,and 79.5% respectvely.100 ng/L as critical value of IFH-γ,they were 83.9%,93.8% and 87.5% respeelively.Combined detection of them in tuberculous pleurisy,the sensitive tale,specinl rate and clinical diagnose accordance rate were 94.5%,97.8% and 94.3% respectively.Conclusion Combined delection of ADA activity,CRP content and IFN-γ content in pleural fluid can improve the diagnosis of tuberculous pleurisy.