Background : Although most patients with tuberculous pleurisy respond well to anti-tuberculous drugs, some are known to progress into severe pleural thickening which needs decortication despite adequate anti-tuberculous treatment. Therefore, the purpose of this study was to identify factors associated with the development of severe pleural thickening in patients who finally underwent pleural decortication in tuberculous pleurisy. Patients and Methods : From retrospective medical records review, 121 patients initially diagnosed as tuberculous pleurisy without initial pleural fluid loculation were enrolled between January 1998 and December 2002. They were separated into two groups: 85 patients in group 1 who improved by anti-tuberculous drugs only, and 36 patients in group 2 who had progressed into pleural adhesion and finally underwent pleural decortication despite adequate (more than 6 months) anti-tuberculous treatment. Results : Males were more common in group 2 (M/F=31/5) than in group 1 (M/F=53/32) (p=0.010). Group 2 patients tended to have lower pleural fluid glucose level ($58{pm}4$ mg/dL) than group 1 ($89{pm}3$ mg/dL) (p=0.001) and higher pleural fluid adenosine deaminase level ($86{pm}5$ IU/L) than group 1 ($76{pm}3$ IU/L), (p=0.038). There were no significant differences in age, symptom duration, pleural fluid amount, or pleural fluid LDH level between groups 1 and 2. Conclusions : There was a relative risk of tuberculous pleurisy progression into severe pleural thickening which needed decortication in the case of male patients, low pleural fluid glucose or high adenosine deaminase level. But further, large-scale, prospective studies should be investigated.