100 patients with histologically and cytologically confirmed intrathoracic space-occupying growths were examined by CT and MR over and above conventional x-ray film diagnosis. MR tomography was performed in all the 100 patients via ECG-triggered T1 and T2 weighted spin echo sequences. The last 35 patients were additionally examined via gradient echo sequences with which it is possible to examined 24 consecutive layers in any layer plane within 7 minutes without ECG triggering. Comparative evaluation of CT and MR tomography yielded an equally high degree of sensitivity when identifying intrathoracic growths. Compared to CT, determination of tumour status via MR tomography proved easier in individual cases. Other advantages of MR tomography were seen in the staging of bronchial carcinomas. Compared with conventional spin echo sequences the rapid gradient echo sequences reduced examination periods by more than 50%. In the cardiac region and the mediastinal structures that pulsate with it the diagnostic value of the gradient echo images is at present slightly impaired by fuzziness caused by movement. The image quality of the spin echo images is comparatively good in the regions of the superior and posterior mediastinum, the lungs and the thoracic wall.