To evaluate the risk factors involving the recurrence of the spontaneous pneumothorax, 125 patients were reviewed. These patients were consecutively diagnosed and treated for the spontaneous pneumothorax at the Department of Thoracic and Cadiovascular Surgery, Yeungnam University Hospital, from Jun. 1986 to Apr. 1991. The patients were divided into two groups, control and recurrent. The control group, consisting of the 125 patients, did not have recurrences of the pneumothorax for a period of 2 years following the first attack. The recurrent group were the remaining 57 patients, who experienced at least one recurrence during the same period. The number of patients over the age of 50 was significantly higher in the recurrent group than the control group. Abnormal findings on chest X-ray[e.g., old tuberculous scar, emphysematous change, visible bullae of blebs] were observed more frepuently in the recurrent group. also, when the pneumothorax size was larger than 50%, and the air-leakage from the chest tube was longer than 3 days during the first attack the incidence of recurrence was significantly increased in the recurrent group. The recurrence occured more frequently in the afternoon, and in the same thoracic cavity. Exertion and smoking were not related to the risk factors in this clinical setting.