Twelve brain-dead patients admitted to the Department of Traumatology, Osaka University Hospital, from July 1988 to August 1989 were studied. A hemodynamic response elicited by passive neck flexion was observed in 10 of the 12 patients. After passive neck flexion, blood pressure began to rise, and the heart rate increased slightly. Blood pressure peaked about 2 minutes after the initiation of neck flexion and then decreased gradually to the baseline level within a few minutes. These responses were suppressed completely by administration of the ganglion blocker trimethaphan camsilate, which suggests that the efferent pathway of the response is mediated by the sympathetic nervous system.