Autotransfusion of blood from the peritoneal cavity of pigs under a regimen of acid citrate dextrose solution 1:10 v/v for reservoir anticoagulation or systemic heparinization with 300 Iu/kg did not affect cardiac performance. Rapid deterioration of left ventricular pump performance was observed when low dose systemic heparin 100 Iu/kg was used. Evidence suggests that this is related to diffuse coagulation.