The Röntgenograms of 456 cases of pulmonary carcinoma were examined on the morphologic alternation of tumor growth, comparing with the pathological findings of 61 cases which were confirmed on operation and autopsy. Especially such cases which happened to have been observed the progress of new growth for a while, were followed up and overtaken, so that the basi cearly diagnosis of the pulmonary carcinoma may be established.<BR>I. The form and localization of the primary origin.<BR>145 cases in which the tumor is less than 3cm in diameter were selected. The well defined nodular or granular forms are the most common. (44.1%). The cases which show the infiltrating linear shadows radiated from hilum are 40%. (Fig. 1, 2) In the early stage when the size of the tumor is small, 45.5% are found in the hilum and 54.5% in lung parenchyma. However, 86.2% of the nodular type of tumor are located in the lung parenchyma and 78.1% of the infiltrating type are in the hilum. (Table 3) Of 10, 942 cases of inflamatory disease which are considered having the relationship with the genesis of pulmonary carcinoma, 8 cases are found to be carcinoma. One should be strict and cautious to confirm the site of genesis of a tumor, if the inflamatory lesion or scav can become the originating ground of a tumor.<BR>II. Growth rate of a tumor.<BR>The growth rate of a tumor in which the size is less than 3 cm was examined. 61 cases which happened to follow up the progress of growth of tumor periodically were selected. The average growth rate in a month is 3 mm. (Table 6)<BR>III. Metamorphosis of the tumor.<BR>The mode of metamorphosis of 86 tumors was roentgenologically investigated and followed up for more than 10 months. The results are shown in Fig. 6.<BR>The cavity formation of pulmonary carcinoma is seen in 38 (9%) out of 418 cases. It was found at about 2 years and 1 month after the first discovery of the tumor. In 2% an early cavity formation was found.<BR>As for the secondary phenomenon, atelectasis, (36.3%), pneumonia (13.5%) and abscess (6%) are shown in order of occurence.<BR>IV. Pathological consideration.<BR>Some patholooical and roentgenological consiedration. were performed with the nodular and infiltrating type of tumor which originated in the hilum and lung parenchyma. Some tumors were found to infiltrate, adhere and encircle the pulmonary vein, and the tumors originated from the subpleural region or adjacent to the mediastinum. (Fig. 10-16)<BR>V. The search for the alveolar cell carcinoma.<BR>43 cases of alveolar cell carcinoma were searched for by means of observing some serial roentgenograms and some specimens of autopsies. 41.8% of them were found having multiple lesions without evident origin, 25.6% multiple lesions with suspicious origin, and 32.6% localized origin. (Fig. 17)<BR>The differentiation of alveolar cell carcinoma as a monopolar originating tumor with multiple intrapulmonary metastases or multipolar originating tumors was not elicited. However, if it were found earlier, the possibility of the determination of its origin would have been increased.