The function of ventilation, total and respective to the right and left lungs, was investigated before and after Various surgical operations in pulmonary tuberculosis, and the following results were obtained. 1) After the operation of thoracoplasty restrictive disturbance of ventilation was proved, which was marked as the number of resected ribs increased, especially to more than five. In tho respective determination, the disturbance was prominent in the operated side,but the contralateral lung exhibited likewise a slight hypofunction. 2) In the course of pulmonary resection, the pulmonary function of the operative side under the spontaneous respiration with intratracheal anesthesia was abolished almost completely coincident with pulmonary collapse. The function, however, recovered gradually according to the re-expansion of the remaining lung induced by the continuous suction of the thoracic cavity following the operation. The variation in th oximetric readings was scarecely found in the course of the operation, with the exception of a marked fall during the intratrcheal suction, especially contralateral intrabronchial suction. 3) In the cases who demonstrated a good re-expansion of the remaining lung after pulmonary resection, better function was kept than in the cases of bad re-expansion. The influence of pleural thickning as well as phrenic motor disturbance was very great, as much as the extent in the case of additional thoracoplasty. 4) The functional disturbance in the cases demonstrating good expansion after pulmonary resection depended on the extent of resection. In the cases undergoing the resection of less than 4 segments, the post-operative function was well maintained, while in some cases of more than 5 segments a pronounced tendency toward pulmonary emphysema was observed, and in the other cases of re-expansion, excessive extension of the lung was recognized. The permissible safety limit was presumed to be less than 4 segments from the stand point of the post-operative re-expansion. 5) As for the necessity of adjunctive thoracoplasty in total pneumonectomy, those cases who did not undergo adjunctive thoracoplasty, especially those who received pneumonectomy on the right side, demonstrated, in general, excessive extension of the remaining lung, therefore adjunctive thoracoplasty is recommendable in the cases of right-side pneumonectomy. As a general rule, however, adjunctive thoracoplasty should not be performed in young persons as well as in women undergoing left-side pneumonectomy. 6) The ventilating function after the decortication for the treatment of tuberculous thoracic empyema and atelectasis depended upon the degree of re-expansion; the improvement in the function was found unexpectedly small. 7) The recovery of vital capecity after various surgical treatment was usually rapid until three months after the treatment, gradual thereafter, and very slow after six months. 8) In seven cases presenting a contralateral vital capacity of 655-1014 cc (the proportion to the standard total value: 15.7-24.2%), segmental resectomy or lobectomy was carried out successfully under the controlled respiration with intratracheal anesthesia. But in general, the safety limit was thought to be about 30 per cent in the proportion of the contralateral lung to the standard total value.