PURPOSE: To determine whether physician specialty influences transfusion threshold in patients with acute severe traumatic brain injury (TBI). METHODS: We surveyed transfusion preferences of chiefs of trauma surgery, chairs of neurosurgery, and surgical and neurosurgical ICU directors at all 187 US Level I trauma centers using a scenario-based, multiple-choice instrument administered by mail. We evaluated the hemoglobin value used as a transfusion threshold for patients with severe acute TBI in several scenarios as well as opinions regarding the rationale for transfusion. RESULTS: The response rate was 58% (312/534). Mean time in practice was 17 +/- 8 years and 65% were board certified in critical care. Neurosurgeons (NS) used a greater mean hemoglobin threshold for transfusion of TBI patients than trauma surgeons (TS) and non-surgeon intensivists (CC) whether the intracranial pressure was normal (8.3 +/- 1.2, 7.5 +/- 1.0, and 7.5 +/- 0.8 g/dL; NS, TS, and CC, respectively, P < 0.001) or elevated (8.9 +/- 1.1, 8.0 +/- 1.1, and 8.4 +/- 1.1 g/dL; NS, TS, and CC, respectively, P < 0.001). All three groups commonly believed that secondary ischemic injury is an important problem following TBI (74, 66, and 63%, P = 0.32), but fewer NS believed that transfusions have important immunodulatory effects (25, 91, and 83%, P < 0.001). CONCLUSIONS: Neurosurgeons prefer more liberal transfusion of TBI patients than TS and CC, suggesting that actual practice may depend largely on which specialist is primarily managing care. The observed clinical equipoise would justify a randomized trial of liberal versus restrictive transfusion strategies in patients with TBI.