The purpose of this investigation was to explore the applicability of repetitive nonsimultaneous and nonsystematic mensuration of the roentgen shadows of malignant neoplasms in the lung to the betterment of our understanding of the growth and behavior of malignant neoplasms in man and a better definition of the limitations of the roentgenographic detection of pulmonary tumors. Material Consecutive patients attended at the Ellis Fischel State Cancer Hospital between 1940 and 1961 and having 2 or more thoracic roentgenograms showing intrathoracic primary or metastatic cancers were included in the study. When multiple thoracic roentgenograms were taken on the same day, only the best study was considered. Roentgenograms taken by some technique other than the standard 72 in. target-film distance, posterioranterior projection, were excluded. Cases meeting the initial conditions included 21 patients having 22 primary pulmonary cancers and 176 patients with cancers metastatic to lung. All roentgenograms were reviewed, and all of