Skeletal involvement occurs in 3-5% of patients with tuberculous infection. Involvement of the sacroiliac joint has been reported up to 9.5% of patients with skeletal involvement, We could not find any classification of the sacroiliac tuberculosis for clinical use in the literature. The purpose of the study was to classify tuberculous sacroilitis newly by radiologic studies and clinical findings and to suggest the appropriate treatment according to each group. For this study, thirteen patients who were treated with tuberculous sacroiltis were reviewed. Radiological findings from the anteroposterior and oblique plain films of the lesion site were compared with those of unaffected site. We also reviewed the computerized tomographs and clinical features for classification and disease progression after treatment. In all patients, the follow up period was more than two years. The classification was as follows ; type I (widening of sacroiliac joint space and blurring of the margin of sacroiliac joint); one case, type II (mild erosion of the sacroiliac joint); three cases, type III (severe destruction of the sacroiliac joint with cyst formation and sclerosis); four cases, Type IV (lesion of sacroiliac joint with inguinal or gluteal abscess and/or other spinal tuberculosis) ; five cases. Cases of the type I and type II had been treated with only antituberculous medication and the cases of the type III and type IV had been treated with curettage, arthrodesis, and antituberculous medication. The fusion of sacroiliac joint was obtained at 23 months after treatment in the paitents with type I or type II lesion, and at 22 months after operation in the patients with type III or type IV lesion. There was no recurrence. The site of the lesion was located lower porion of the sacroiliac joint. The destruction and sclerosis of ilium was more severe than that of sacrum in all cases. The drainage of abscess, curettage, and arthrodesis were appropriate treatments for type III and type IV lesion of the our new classification. The surgery increases the local effect of the antituberculous medication and offers pathological diagnosis. In conclusion, the new classification was suggested to be helpful to decide the treatment regimen.