To compare different doses of tranexamic acid, 150 consecutive children with congenital cyanotic heart disease were randomly assigned to one of 5 groups of 30 each. Group A served as a control. Group B received 50 mg.kg(-1) of tranexamic acid at induction of anesthesia. Group C received 10 mg.kg(-1) at induction followed by an infusion of 1 mg.kg(-1).h(-1). Group D had 10 mg.kg(-1) at induction, 10 mg.kg(-1) on bypass, and 10 mg.kg(-1) after protamine. Group E had 20 mg.kg(-1) at induction and again after protamine. The control group had the longest sternal closure time, the greatest blood loss in the first 24 hours, and the highest requirements for blood and blood products. Among the 4 groups given tranexamic acid, group D (triple dose) had the best results, followed by group E (double dose). Group B (single dose) had the worst results among the groups receiving tranexamic acid.