Reexamination was made on the gas components in the arterial blood of far advanced pulmonary tuberculosis cases at rest during air breathing. The effects of intermittent positve pressure breathing (I. P. P. B. ) on these cases were evaluated, on the basis of arterial oxygen saturation used as index. Also, the effects of pure oxygen breathing and exercise on their gas components, were studied.The results obtained were as follows:1. The arterial oxygen saturtion at rest, in 23 of 51 cases (45.1%) was below normal limits. The arterial oxygen content for 51 cases on an average was as low as 13.08 vol. %, while their arterial carbon dioxide content was within normal limits (49.33 vol. %). The oxygen capacity was generally low indicating anemia. The above findings suggest the necessity of consideration for anemic anoxia. It does not seem always reasonable to diagnose anoxic anoxia only on arterial oxygen saturation in cases with far advanced pulmonary tuberculosis as seen in the present study. The % VC was low, its average value being 40.0%.Concerning correlations between electrocardiographic, phonocardiographic findings and variations of arterial blood gas components, all cases with any phonocardiographic change belonged to an abnormal group of electrocardiogram except for two cases which showed only an accentuated second pulmonary sound. These two cases showed a normal oxygen saturation and a decrease of the oxygen content and oxygen tension in the arterial blood. About half the abnomal group of electrocardiogram revealed a decrease of arterial oxygen saturation, especially, of the arterial oxygen content. In 71.4% of that group, arterial carbon dioxide tension was found decreased and in 54.3% of it respiratory acidosis was observed or suggested.2. Following the treatment of I. P. P. B., oxygen saturation in the arterial blood was improved in 8 of 11 cases (72.8%), but three cases were found unresponsive because of their aggravated clinical course, resulting in the fatality of two cases. The results of the treatment were followed for five months revealing its effect still continuously working. One case which apparently did not respond to the treatment showed a 4.12% improvement of arterial oxygen saturation in five months over the stage immediately after the treatment.3. Two cases (9.1%) which failed to reach a 100% arterial oxygen saturation following a 100% oxygen inhalation, that is, cases which indicate the presence of anatomic venous admixture, showed their arterial oxygen saturation at rest to be below normal (92.0%).4. Although the cases studied were comparatively few, all of them showed a decrease of arterial oxygen saturation after their physical exercise, most of the cases revealed a trend of decrease in the arterial oxygen content.Cardiac output of these cases increased by 2∼2.5 times over the pre-exercise period