Author studied the possible pathogenesis of spontaneous pneumothorax and its effective treatment in 33 cases, and the results obtained as follows: 1] Of the 33 cases, 15 cases were originated from pulmonary tuberculosis, 11 cases were non-tuberculous natures and 7 cases were followed by traumatic chest injuries which were not associated with a laceration of the lung or rib fractures. 2] So called "Idiopathic spontaneous pneumothorax" seemed mostly to be caused by rupture of the emphy- sematous blebs. 3] Spontaneous pneumothorax,in process of the pulmonary tuberculosis, seemed to be caused by the rupture of blebs which was formed with a pathological process of chronic pulmonary tuberculosis. 4] Author experienced interesting cases of giant blebs which had been fully occupied the right thoracic cavity. At first, it was misdiagnosed as extensive spontaneous pneumothorax on X-ray which was revealed extensive pleural air shadow with total atelectasis of the right lung. A pneumonectomy was performed together with the giant multiple blebs. 5] Generally, closed thoracotomy with water-sealed drainage is the treatment of choice in spontaneous pneumothorax. However,open thoracotomy and adequate surgical procedures should be undertaken in patients with continuous air leakage or recurrent attack of spontaneous pneumothorax.[KTCS 1968;1:11-18]