This report is an analysis of 43 cases of primary mediastinal tumors and cysts which were treated in the Department of Thoracic and Cardiovascular Surgery, Tae Jeon Eul li General Hospital from January, 1986 to April, 1995. There were 19 males and 24 females, and their ages ranged from 4 years to 68 years, with mean age of 31.3 years. The most common symptoms were dyspnea 48.8%, chest disconyort 39.5%, cough )4.9%, and chest pain 23.3%, and the most frequently encountered location of tumor was anterior mediastinum followed by posterior, and middle mediastinum. From the pathologic viewpoint, teratoma was the most frequent type followed by neurogenic tumors, cysts, thymoma, and Iymphoma. The most useful diagnostic method was plain X-ray examination of the chest, and final diagnosis could usually be made only after an operation. All of benign tumors were completely removed and malignant tumors were treated with chemotherapy and radiotherapy after operation There were 7 (16.3 %) cases of postoperative complications, and there was no postoperative mortality.