The operative findings at 27 thoracotomies in 24 patients were compared with the results of chest X-rays, computerized tomographies and conventional tomographies. Radiological and operative findings corresponded in 15 of 27 cases. The computerized tomography proved to be the most sensitive method for the estimation of the number of metastases. The foci often located close to the pleura repeatedly cause an exudative reaction of the visceral pleura and thus mark the interlobular septa. These changes were most distinctly recognized by conventional tomography and gave indications for the topographic classification of the metastases. Despite the careful evaluation of the imaging techniques small metastases were often not detected.