Basic plasma coagulation function is readily assessed with a few simple in vitro laboratory tests, prothrombin time (PT) and partial thromboplastin time (PTT), and they are useful as the current standard for establishing a diagnosis of coagulopathy. While PT and PTT have been proven as predictors of adverse outcomes, including severity in acute traumatic coagulopathy (ATC), they are not always accurate predictors of bleeding risk and may not provide precise ongoing assessment of the coagulation dysfunction in a trauma patient undergoing resuscitation. Nevertheless, as point-of-care tests are being developed, validated, and made widely available in trauma care settings, PT and PTT remain the most cost-efficient and easily available tests for early coagulopathy assessment in trauma patients. In the absence of more robust testing, clinicians should suspect and empirically treat acute coagulopathy in trauma patients. New and evolving tests such as thromboelastography and rotational thromboelastometry may be better able to guide ongoing therapy and transfusion management in trauma patients.