Tuberculous cavity is important in diagnosis and observation in the course of pulmonary tuberculosis. Authors anlayzed the radiologic findings of cavity and average months of negative conversion in AFB culture in 89 cases of initial treatment. The results were as follows : 1. The more number of cavities, the longer period in negative conversion of AFB culture. 2. No relation between sums of diameter and thickness of cavity and average months of negative conversion in AFB culture. In the cases of cavity with air-fluid level took longer period in negative conversion of AFB culture than those of cavity without air-fluid level, significantly. 4. No relation between radiolgic findings of cavity and results of chemotherapy for pulmonary tuberculosis.