This report is an analysis of 183 cases of mediastinal tumors which were experienced in the Department of Thoracic and Cardiovascular Surgery, Yonsei Medical Center from January 1960 to June 1985. In this series, teratoma and neurogenic tumors were found to be the most frequent tumors [24.0%] histopathologically. Male to female sex distribution was 1.2 to 1 with the male predominant. The main clinical symptom was dyspnea, and there was no definitive symptom in 10.9% of all cases. In operating, all of the benign tumors were removed. The most frequent complication was wound infection. [13.7%].