Patients on warfarin are at high risk for potentially life-threatening hemorrhage even after relatively minor trauma. Outcomes of these patients and the potential complications of reversing the effects of anticoagulation have received little attention. This study was performed to determine the overall outcome of orally anticoagulated patients who sustained injury as well as to determine any untoward effects of reversing their anticoagulated states. A retrospective study of injured patients on warfarin was conducted on patients admitted to an urban, university, tertiary-referral, level I trauma center between 1/1/93 and 12/31/96. Surviving patients were followed for a period of at least 1 month. Injuries were grouped by anatomic site. Charts were reviewed for degree of anticoagulation on admission (ie, initial international normalized ratio [INR]), survival, adverse effects of reversal of anticoagulation, and reinstitution of warfarin therapy. Discharged patients were contacted at home for follow-up. Thirty-five consecutive patients, 18 men and 17 women, on warfarin therapy at the time of their injuries were reviewed. The mean age was 75 years, with a range of 39 to 96. The mean follow-up period was 12.7 months. Reasons for anticoagulation included atrial fibrillation, prosthetic heart valves, revascularized limb, hypercoagulable state, deep venous thrombosis, pulmonary embolism, phlebitis, and aortic stenosis. Mean admission INR was 3.2, with a range of 1.6 to 10.0. There were 8 in-hospital deaths. Intracranial hemorrhages accounted for the majority of injuries. Ten patients were not given reversal therapy. Four complications were attributable to reversal therapy (upper extremity hemiplegia, transient ischemic attack, deep venous thrombosis, arterial thrombosis). Twenty-one patients had their warfarin reinstituted. Follow-up of surviving patients ranged from 1.5 to 42 months. Patients on warfarin are at high risk for intracranial hemorrhage following trauma. Patients on warfarin may be reversed during the acute period following injury, but transient complications may arise. Further prospective studies need to be conducted to determine which anticoagulated trauma patients may not require reversal therapy.