Fifty-two cases of spontaneous pneumothorax encountered in Seoul National University Hospital during the period from 1961 to 1968 were reviewed. The incidence was highest in the adult between 21 and 40 years of age, showing 50%. Four cases of bilateral spontaneous pneumothorax [7.7%] were noted. Pulmonary tuberculosis was the most common cause, 50% of the cases. Non-tuberculous group was 26 cases [50%], of which 15 cases were idiopathic, 5 emphysematous bullae or blebs, 5 inflammatory lung disease, mostly pneumonia, and one pulmonary paragonimiasis. Among 52 cases, the lung expanded completely with absolute bed rest in 7 cases, 3 out of 9 with needle aspiration and bed rest, 34 out of 41 with closed thoracotomy and underwater seal Stedman suction, and 7 cases were treated with open thoracotomy with resection of the lesions without complication. Among these cases treated with closed thoracotomy it took about 3 days in non-tuberculous group to expand the collapsed lung and more than 2 weeks in tuberculous group.[KTCS 1968;1:25-30]