The patient with findings of diffuse infiltrative lung on chest X-ray has various causes; therefore, the prognosis is different and the treatment should be changed according to the cause. We are trying to identify the meaning of operative lung biopsy and to 11nd a more accurate and effective procedure. We reviewed 46 medical records of patients with the findings of diffuse infiltrative lung on chest X-ray who had undergone operative lung biopsy or biopsies for 8 years. The open lung biopsy were done in 22 cases(47.8%) and thoracoscopic lung biopsy in 24 cases(52.2%). There is no significant difference in the rate of diagnosis(p=0.452) and the incidence of complications(p=0.155) between these groups. The number of cases with more than two biopsies are 9(19.6%) and that of one biopsy are 37(80.4%). There are no statistical difference in the rate of diagnosis(p=0.928) and the incidence of complications(p=0.125). The postoperative complications occurred in 8 cases,7 cases of air leak more than 7 days and 1 case of respiratory insufficiency. In the diagnosis and treatment of the patients with findings of infiltrative lung on chest X-ray, the operative lung biopsy is the very necessary course, and shows satisfactory rate of diagnosis with negligible complications.