Hexadimethrine bromide was used for the neutralization of heparin during cardiac surgery in the late 1950s. For some years, this institution has used it for patients who may be allergic to protamine. In view of the recent renewal of interest in hexadimethrine, we present four cases outlining its use during cardiac procedures in such patients. Other drugs for reversing the action of heparin such as heparinase or platelet factor IV are not yet widely available.