Thromboelastography(TEG) is the measure of viscoelastic properties of blood coagulation by providing informations on the interactions of all the coagulation precursors and gives more clinically useful information on coagulation than that available from routine coagulation tests or activated coagulation time(ACT). TEG is simple to use and can be performed within 30 minutes of blood sampling. We evaluated whether epsilon aminocapric acid(EACA), 1-deamino-8-D-arginine vasopressin (DDAVP) and platelets can improve coagulation in vitro after cardiopulmonary bypass(CPB) by TEG in 24 cases including 13 long bypass group(Mean bypass time: 127±24 min.) and II short bypass group(Mean bypass time: 47±15 min.). The results as follows: 1) Maximum Amplitude(MA) and/or Alpha angle 20 min. after protamine neutralization in both groups were more depressed than those of before CPB, but 3 hours after protamine neutralization, MA was improved back to the values of before CPB without improving in long bypass group. 2) We couldnt find any evidence of statistical significance that EACA or DDAVP improved eoagulation state after CPB in vitro test, but in some cases EACA or DDAVP improved the coagulability by TEG. 3) In vitro test of fresh platelet solution, platelets shortened R time and increased MA and alpha angle and thus improve the coagulation status 20 min. after protamine neutralization in longer CPB groups. And platelets improved TEG findings in short CPB group without statistical significance. From above results, we could evaluate the depressed coagulation state by TEG and by in vitro test of drugs or blood products, abnormal coagulation states of cardiopulmonary bypass patient can be corrected accordingly.