In 20 normal cases and 39 pulmonary tuberculosis cases, regional pulmonary arterial blood flow measurement and lung perfusion scans by 131I-Macroaggregated albumin, lung inhalation scans by colloidal 198Au and spirometries by respirometer were done at the Radiological Research Institute. The measured lung function tests were compared and the results were as the following:1) The normal distribution of pulmonary blood flow was found to be 54.5¡¾2.82% to the right lung and 45.5¡¾2.39% to the left lung. The difference between the right and left pulmonary arterial blood flow was significant statistically (p<0.01). In the minimal pulmonary tuberculosis, the average distribution of pulmonary arterial blood flow was found to be 52.5¡¾5.3% to the right lung and 47.5¡¾1.0% to the left lung when the tuberculous lesion was in the right lung, and 56.2¡¾4.4% to the right lung and 43.8¡¾3.1% to the left lung when the tuberculous lesion was in the left lung. The difference of pulmonary arterial blood flow between the right and left lung was statistically not significant compared with the normal distribution. In the moderately advanced pulmonary tuberculosis, the average distribution of pulmonary arterial blood flow was found to be 26.9¡¾13.9% to the right lung and 73.1¡¾13.9% to the left lung when the tuberculous lesion was more severe in the right lung, and 79.6¡¾12.8% to the right lung and 20.4¡¾13.0% to the left lung when the tuberculous lesion was more severe in the left lung. These were found to be highly significant statistically compared with the normal distribution of pulmonary arterial blood flow (p<0.01). When both lungs were evenly involved, the average distribution of pulmonary arterial blood flow was found to be 49.5¡¾8.01% to the right lung and 50.5¡¾8.01% to the left lung. In the far advanced pulmonary tuberculosis, the average distribution of pulmonary arterial blood flow was found to be 18.5¡¾11.6% to the right lung and 81.5¡¾9.9% to the left lung when the tuberculosis lesion was more severe in the right lung, and 78.2¡¾8.9% to the right lung and 21.8¡¾10.5% to the left lung when the tuberculous lesion was more severe in the left lung. These were found to be highly significant statistically compared with the normal distribution of pulmonary arterial blood flow (p<0.01). When both lungs were evenly involved the average distribution of pulmonary arterial blood flow was found to be 56.0¡¾3.6% to the right lung and 44.0¡¾3.2% to the left lung. 2) Lung perfusion scan by 131I-MAA in patients with pulmonary tuberculosis was as follows:a) In the pretreated minimal pulmonary tuberculosis, the decreased area of pulmonary arterial blood flow was corresponding to the chest roentgenogram, but the decrease of pulmonary arterial blood flow was more extensive than had been expected from the chest roentgenogram in the apparently healed minimal pulmonary tuberculosis. b) In the pretreated moderately advanced pulmonary tuberculosis, the decrease of pulmonary arterial blood flow to the diseased area was corresponding to the chest roentgenogram, but the decrease of pulmonary arterial blood flow was more extensive in the treated moderately advanced pulmonary tuberculosis as in the treated minimal pulmonary tuberculosis. c) Pulmonary arterial blood flow in the patients with far advanced pulmonary tuberculosis both before and after chemotherapy were almost similar to the chest roentgenogram. Especially the decrease of pulmonary arterial blood flow to the cavity was usually greater than had been expected from the chest roentgenogram. 3) Lung inhalation scan by colloidal 198Au in patients with pulmonary tuberculosis was as follows:a) In the minimal pulmonary tuberculosis, lung inhalation scan showed almost similar decrease of radioactivity corresponding to the chest roentgenogram. b) In the moderately advanced pulmonary tuberculosis the decrease of radioactivity in the diseased area was partly corresponding to the chest roentgenogram in one hand and on the other hand the radioactivity was found to be normally distributed in stead of tuberculous lesion in the chest roentgenogram. c) In the far advanced pulmonary tuberculosis, lung inhalation scan showed alomst similar decrease of radioactivity corresponding to the chest roentgenogram as in the minimal pulmonary tuberculosis. 4) From all these result, it was found that the characteristic finding in pulmonary tuberculosis was a decrease in pulmonary arterial blood flow to the diseased area and in general decrease of pulmonary arterial blood flow to the diseased area was more extensive than had been expected from the chest roentgenogram, especially in the treated group. Lung inhalation scan showed almost similar distribution of radioactivity corresponding to the chest roentgenogram in minimal and far advanced pulmonary tuberculosis, but there was a variability in the moderately advanced pulmonary tuberculosis. The measured values obtained from spirometry were parallel to the tuberculous lesio in chest roentgenogram.