Between January 1978 and March 1981, 100 anterior mediastinotomies were performed in patients with proven or suspected lung cancer. It was done 72 times in patients with a tumor of the left lung, all presenting with a normal mediastinum. Of those 72 patients, 59 had a tumor in the left upper lobe: 30.5% of the latter were found to have involved mediastinal lymphnodes (our yield in this location was 15.1% when using the cervical mediastinoscopy); 16 patients with a left upper lobe tumor had both an anterior negative cervical mediastinoscopy followed by an anterior approach: 4 became positive (25%). The anterior mediastinotomy was performed two times in patients with a suspect mediastinum: the mediastinoscopy was once positive, and once negative. It was done 26 times in patients with a radiologically manifest enlarged mediastinum (7 on the right side, 19 on the left side); in 24 patients the histological diagnosis was unknown. The anterior mediastinotomy was positive in all 26 cases. For the whole group we found positive nodes in 10 of 26, i.e. 38.5% of the patients despite normal findings at cervical mediastinoscopy. We would therefore recommend an anterior mediastinotomy in every patient with a suspect or an enlarged superior mediastinum in order to establish an histological diagnosis or exceptionally to check the operability. If the mediastinum is radiologically normal, the anterior approach has much more chance to yield a positive result than the cervical one when the tumor is located in the left upper lobe.