This report is a review of 98 cases of the primary mediastinal tumors which are treated in the Department of Thoracic and Cardiovascular Surgery, Chonnam University Hospital from January, 1985 to February, 1993 and divided two groups. One group is from January, 1985 to January, 1989 and named it Group 1[G1]. Another group is from February, 1989 to February, 1993 and named it Group 2[G2]. Chest pain is the most common clinical manifestation in the two groups. The common mediastinal tumors are teratoma 11 cases[29.7%], neurogenic tumor 7 cases[18.9%], thymoma 6 cases[16.2%], primary cyst 3 cases[8.1%] in Group 1 and thymoma 16 cases[26.2%], teratoma 15 cases[24.6%], neurogenic tumor 9 cases[14.8%], primary cyst 9 cases[14.8%] in Group 2. Therefore this result shows that the incidence of thymoma is increased in group 2. In benign tumors, the subjective symptoms are 64.3% in group 1 and 63.6% in group 2. In malignant tumors, they are 100% in group 1 and 82.4% in group 2. this result shows that asymptomatic malignant tumors are increased in group 2. The successful excision is done in all of the 71 benign tumors except one. In malignant tumors, the complete surgical excision is increased from 11.1% in group 1 to 41.2% in group 2.