In 10 Skoliose-patients undergoing Harringtons-Operation, measurements of the oszillatory impedance and arterial blood gases were made intraoperatively. The resistance was elevated from the beginning without any change during the operation. The phase was in the inductive range with a further deviation during increasing extension. The possible reasons are the maximal rigidity of thorax and/or parenchyma or change in tracheobronchial "arborisation". Increase in dead space or changes in ventilation-perfusion ratio are suggested by the blood gas measurements. Further investigations will be necessary to determine, if the impedance of the lung is of value in determining the amount of intraoperative extension or postoperative lung function.