A clinical evaluation was performed on 56 patients[ 60 cases ] of open thoracotomy in spontaneous pneumothorax who were admitted and treated at department of Thoracic and Cardiovascular Surgery, Chung Ang University, Yong San Hospital during the past 3 years from March 1990 to February 1993. The results were as follows. 1. The sex ratio was male predominence [ M:F = 7:1 ]. 2. The most common age group were 2nd, 3rd decades. 3. The most common chief complaints were dyspnea and chest pain [46.3% ]. 4. The etiologic factors of spontaneous pneumothorax were primary spontaneous pneumothorax [ 78.3%], secondary tuberculosis [ 18.3%], and others [ 3.4% ]. 5. The site of spontaneous pneumothorax was 50% in right, 40% in left, and 10% in both. 6. The state of activity on attack was almost in the usual life [ 98.3% ]. 7. Average height was 172.5 $pm$ 5.39 cm in male and 164.0 $pm$ 3.51 cm in female, average weight was 59.1 $pm$ 7.06 kg in male and 52.0 $pm$ 4.97 kg in female. 8. The common indications of open thoracotomy were recurrence [ 34.4% ] and persistent air leakage [ 17.8% ]. 9. The operative procedures were bullectomy [ 73.3% ], partial resection [ 11.7% ], lobectomy [ 11.7% ], and others [ 3.3% ]. 10. The most frequent location of bulla or bleb were apical segment of RUL [ 43.3 % ] and apicoposterior segment of LUL [ 40.0% ]. 11. The number of visible bulla or bleb were mainly 1 to 5, and size was about 1 to 3 cm.