BACKGROUND: The routine application of the combined regimen of corticosteroid-antituberculosis therapy to the tuberculous pleurisy remains controversial. Steroid therapy to tuberculous pleurisy could be effective on the acceleration of absorption of pleural effusion and symptom improvement, but there has been debate about the effect of prednisolone on the prevention of pleural adhesion. So we studied the efficacy of combined regimen of prednisolone-antituberculosis therapy on the absorption of pleural effusion and prevention of pleural adhesion. METHODS: A prospective, randomized study was performed in 82 patients, 50 patients(non-steroid group) were treated with only antituberculosis regimen for 6 months and in 32 patients(steroid group) prednisolone(30mg/day) were administered in addition to antituberculosis regimen for one months and tapered for another month. The amount of pleural effusion was compared at the beginning of treatment, 2nd month, 6th month and final visit with chest X-ray findings which were graded from grade 0(complete absorption) to grade 6(near total haziness). RESULTS: The amount of pleural effusion of steroid group at 2nd month, 6th month and final visit was lesser than that of non-steroid group (P<0.05). The incidence of the complete absorption of the pleural effusion was 3/32(9.4%) in steroid group, 1/50(2%) in non-steroid group at 2nd month after treatment; and 12/32(37.5%) in steroid group, 6/50(12%) in non-steroid group at 6th month after treatment (P<0.05). At final observation, the incidence of residual pleural thickening was 15/32(47%) in steroid group and 37/50(74%) in non-steroid group (P<0.05). No serious side effects were noted during the treatment with prednis olone. CONCLUSION: The administration of prednisolone in conjunction with antituberculosis chemotherapy improved the absorption of pleural effusion and decreased the residual pleural thickening.