A clinical and radiological study was done on 96 cases of spontaneous pneumothorax, encountered in the Dept. of Radiology, Busan National University Hospital during last 3 years from March. 1979 to March 1982. The results were summarized as follows: 1. In the age distribution, the ages between 20 and 39 years were most highest, as 54 cases (56.3%). In the sex distribution, the ratio of male to female was 5:1 in male predominance. 2. The underlying pathology of the total 96 cases of spontaneous penumothorax were of tuberculous origin in 33.3% and non-tuberculous origin in 66.7%. And below 20 years, most were of non-tuberculous origin. 3. In the cases of lung collapse over 2/3, non-tuberculous origin was more than tuberculous origin and had characteristics of significant mediastinal shifting, in contrast to lower percentage of fluid level by chest radiography. 4. The rupture of blebs or bullae was the main immediate cuses of spontaneous pneumothorax, independent of the underlying pathology. 5. In only 27 cases (28.1%) among total 96 cases, bullae or blebs could be detected on the chest radiography. 6. In treatment of spontaneous pneumothorax, the closed thoracotomy with under water seal drainage is accepted to be the general method of treatment. But open thoracotomy is considered as the best useful therapeutic procedure to prevent the recurrence, whenever bullae or blebs are found on the chest radiography. 7. In the cases of closed thoracotomy, the recurrent rate was 25.0% and most cases were found at ipsilateral side of the first attack. 8. Within a week, the collapsed lung were well expanded in most cases of total 96 cases, after closed thoracotomy.