For the purpose of evaluation of clinical characteristics and histopathological properties in mediastinal tumor, and to provide the guidelines of surgical management of mediastinal tumor,238 patients with mediastinal tumors treated during the period from January 1983 to December 1991 were reviewed at Seoul National University Hospital. There were 106 males & 132 females, and their ages ranged from 3 months to 73 years, with average 33.6 years. The most frequently encountered tumor site was anterosuperior mediastinum followed by posterior, and middle mediastinum. In the pathological viewpoint, thymoma was the most frequent type followed by neurogenic tumor. 81% of the tumor were benign and 19% were malignant. Half of the malignant tumors were neurogenic tumors. Malignancy rate was high in pediatric patients compared to adults as 40% and 19% respectively. 65% of patients were asymptomatic at diagnosis.There was no operative mortality. Post operative complications were occurred in 35 cases. Most frequent complications were adjacent peripheral nerve injuries. But other usual operative complications, such as bleeding, chylothorax, infection, were relatively rare.