The authors report on 29 surgical operations on the descending thoracic aorta, where partial extra-corporal circulation was established between the pulmonary and femoral arteries, using a straight Rigg's cannula inserted into the pulmonary artery. The blood flow rate in the shunt was of the order of 1,5 l/min. Owing to the ease with which the cannula is inserted and removed and to the possibility of switching to total extra-corporeal circulation the authors prefer this technique to all other types of partial derivation.