To evaluate the therapeutic effect of various drug combination in experimental pneumoconiosis, a total of 240 Spraque-Dawley was instilled intratracheally by 50 mg free silica or coal dust with 0.8 ml normal saline. In the control group, it was intratracheally instilled only dust at once, while from l1th week experimental groups were administered drug. Experimental groups were divided into 8 groups according to drug combination such as group treated with piperazine and aspirin, piperazine and allopurinol, piperazine and azathioprine, aspirin and allopurinol, aspirin and azathioprine, allopurinol and azathioprine, solumedrol, and solumedrol and cyclophosphamide. The duration of treatment was 10 weeks. All animals were killed at 20th week after dust instillation. We observed body weight at 20th week after dust instillation, the dry lung weight of left lung, total and differential cell count in bronchoalveolaT lavage (BAL) fluid. Leukotriene B4, tumor necrosis factor, and superoxide anion production from alveolar macrophage, amount of hydroxyproline in left lung, and the histopathologic examination in the right lung stained with hematoxylin-eosin and Masson's trichrome.