For the purpose of evaluation of clinical characteristics and histopathological properties in mediastinal tumors, 130 patients with mediastinal tumors treated during the period from 1958 to 1982 were reviewed. Cancers of unidentified primary site of origin, nonneoplastic lesions and the cases with clinical diagnosis only were excluded from this report. There were 69 males and 61 females, and their ages ranged from 2 months to 66 years, with the average age of 31.3 years. 19.2% of patients were younger than 15 years of age. The most frequently encountered tumors were teratodermoids, followed by neurogenic tumors, thymic tumors, benign cysts, malignant lymphomas and miscellaneous tumors in order of decreasing frequency. 75.4% of the mediastinal tumors were benign and 24.6% were malignant. 16.6% of the patients were asymptomatic at admission. There were 2 postoperative deaths with 1.7% of operative mortality rate, and 2 other deaths who were not operated upon, showing overall hospital mortality rate of 3.1%. Postoperative follow up was possible in 84 cases, and there were 4 late deaths.[KTCS 1983;4:563-570]