The use of blood products in 1480 consecutive cases of adult cardiac surgical procedures over a period of 15 mth was studied retrospectively using the database of the Department of Anaesthesia of the Institut de Cardiologie de Montréal. Use of blood products was compared in patients having (1) coronary artery bypass grafting, (2) valvular surgery, (3) or a combination of 1 and 2. First operations were compared with reoperations. Overall, the use of homologous blood products was greatest in patients of Group 3, intermediate in patients of Group 2, and smallest in patients of Group 1. Reoperations were associated with an increase in intraoperative transfusion of packed red blood cells, but postoperative chest drainage was similar to first operations. When all blood products (packed red blood cells, fresh frozen plasma and platelets) were taken into consideration, patients undergoing primary CABG or valve surgery were the least exposed to homologous blood donors (five and six units transfused respectively). Repeat CABG was associated with an intermediate exposure to homologous blood products (eight units). Finally, primary and repeat combined procedures, and repeat valve surgery were associated with the greatest exposure to foreign blood products (10, 13 and 10 units respectively). The data presented in this study provide a rational basis for stratification of procedures according to the expected use of blood products, particularly in view of future studies which may be planned to examine the efficiency of blood conservation strategies.