Ventilatory functions and arterial respiratory gases were studied in 24 patients who underwent resectional surgery for pulmonary tuberculosis. Postoperative measurements were made 24 hours, 72 hours and 7 days after surgery and the results were compared to preoperative values. Twenty-four hours postoperatively, there occurred striking increase in respiratory rate, minute ventilation, dead space ventilation and dead space tidal volume ratio, and the increase in minute ventilation was caused primarily by the increase in respiratory rate. However, alveolar ventilation, oxygen consumption, carbon dioxide elimination and respiratory quotient showed no significant posto-perative changes although two of the last values showed slight decreases 24 hours after surgery. The lowest arterial oxygen saturation level was obtained 24 hours postoperatively followed by gradual rises but not to the preoperative levels until 7 days after surgery. A decreased arterial carbon dioxide tension with elevated pit was noted 24 hours after surgery, which returned to the preoperative level on the following measurement.[KTCS 1973;1:7-14]