Objectives:To measure fibrinolytic activity in the patients with tuberculous pleurisy and to evaluate the relationship between the effusion levels of these fibrinolytic components and the development of residual pleural thickening(RPT) in these patients. Methods:The plasma and effusion levels of PAI-1,D-D and t-PA were measured using an enzyme linked immunosorbent assay(ELISA)in 41 patients with TB,39 patients with lung cancer,11 patients with heart failure. pleural thickening was measured and defined as a pleural thickness of 10 mm found on chest radiographs at the completion of anti-TB chemotherapy in tuberculous pleurisy patients. Results:There was no significant difference in plasma PAI-1,t-PA and D-D levels among three diseases groups(P > 0.05). Tuberculosis exudates had significantly higher values for PAI-1 and lower values for t-PA than malignant exudates and transudate effusion caused by heart failure(P < 0.05). There was no significant difference in effusion D-D level in three groups(P > 0.05). Significantly higher levels of PAI-1 and significantly lower values of t-PA in effusions were found in patients with RPT than those in patients without RPT(P < 0.05). Conclusion:The release of PAI-1 increased while t-PA level decreased in TB pleural effusions. The imbalance of PAI-1 and t-PA may result in the development of pleural thickening in patients with TB pleurisy. Detection of pleural fluid D-dimer levels has no help in the differential diagnosis of an effusion.