1) The endotracheal anesthesia of closed circulation type was applicated to 259 cases and Hexamethonium bromide (C(6)) and inclining of the operating table were used for 30 cases of pulmonary resection. 2) The dose of C(6) for the artificial hypotensive operation was on the average of 63 mg and the maximum descending of blood pressure was on the average of 34% . Generally we got to the aimed hypotention by the intravenous injection of C(6) 50 mg and inclining of the operating table. But the additional intravenous injection of C(6) did not effected so strongly as the first one. 3) The mean amount of the lost blood in the hypotensive group less than half of that in normal groups. In the hypotensive group there was a tendency to decrease the bleeding even in those cases, in which we could not get the aimed hypotension. 4) The blood and saline used during pneumectomy for hypotensive group, were less than half of those used in the normal group. 5) The tendency of postoperative bleeding as a complication was stronger in the hypotensive group. In one hypotensive case we could only make thoracotomy, because of hypoxia, but in other cases we found no noted complication.