Carbon monoxide derived from carbon monoxide releasing molecules (CORMs) has been demonstrated to enhance normal plasma thrombus speed of growth and strength in vitro. We tested the hypothesis that tricarbonyldichlororuthenium (II) dimer (CORM-2) improves the velocity of formation and strength of hemophiliac plasma thrombi as determined by thrombelastography. Plasma deficient (<1% normal activity) in factor VIII (FVIII; n = 11 individuals), factor IX (FIX; n = 5 individuals) or factor VII (FVII; n = 4 individuals) was exposed to 0 or 100 μmol CORM-2, with coagulation initiated with tissue factor. Coagulation kinetics were monitored with thrombelastography for 15 min. Paired t-tests were used to analyze FVIII-deficient plasma results; relative change was used to describe the other plasma types tested. In FVIII-deficient plasma, CORM-2 exposure significantly (P < 0.05) increased the velocity of thrombus formation (84%) and strength (48%) compared with plasma not exposed to CORM-2. FXI-deficient clots demonstrated an increase in velocity of formation (63%) and strength (43%) after CORM-2 exposure. Lastly, CORM-2 exposure increased FVII-deficient plasma velocity of formation (45%) and strength (63%). CORM-2 markedly enhanced the velocity of clot growth and strength in hemophiliac plasma. These findings serve as the rationale to determine whether CORMs could be utilized as hemostatic agents. © 2010 Wolters Kluwer Health | Lippincott Williams & Wilkins.