Severe bronchospasm at the termination of cardiopulmonary bypass is an unusual but dangerous complication of open-heart surgery. We report two cases. In both of them the final etiology remained unsettled. In one of the cases vigorous and immediate bronchodilatory therapy resulted in a favourable remission. In the second case bronchospasm contributed to a very harmful bulging of the left lung through the opened mediastinal pleura, stretching and damaging the left internal mammary artery graft, which obviously contributed to the fatal outcome. We emphasize especially the following points: 1) a carefully evaluated medical history of patients scheduled for open-heart surgery may reveal some details pointing to an increased risk of bronchospasm during cardiopulmonary bypass; in such cases prophylactic measures may be indicated; 2) immediate vigorous bronchodilatory therapy early at the onset of bronchospasm during the weaning from cardiopulmonary bypass may reverse the alarming situation.