A massive transfusion protocol (MTP) in which most non-RBC transfusions were laboratory result-driven was updated to a 1:1:1 RBC/plasma/platelet formula-driven protocol. Platelet count, fibrinogen level, and prothrombin time (PT) were monitored. In the patients who survived the first 12 hours, the results of coagulation tests were analyzed. Irrespective of the MTP or transfused RBC/plasma ratio, a majority of patients became coagulopathic, usually within the first 2 hours, and a fibrinogen deficiency (fibrinogen level, <100 mg/dL [2.9 μmol/L]) was almost always the initial abnormality. The laboratory value trends under each MTP were indistinguishable: PTs were prolonged and platelet counts and fibrinogen levels fell during the first 100 minutes and then corrected back toward baseline. More than 80% of patients in each group were noncoagulopathic at 12 hours. A 1:1:1 formula-driven MTP did not affect the frequency, nature, or duration of coagulopathy according to laboratory test results.