From 1965 to 1973, 82 patients were operated on for mediastinal tumor. 42.7% of them were incidental radiological findings. Preoperatively, 66% of the mediastinal tumors were not morphologically confirmed. The lethality of the operation was 1.22%. Thymomas (29.3%) were the most frequent findings. 34.2% were malignant. While most patients with benign mediastinal tumors are cured by the operation, the 5 year survival rate for those with malignant tumors was 22%. Further special investigative procedures should only follow a guiding survey radiography in two planes if they can be expected to provide essential information on operability, operational tactics and approach.