The histories of 444 patients admitted to this spinal cord injury service were reviewed for the incidence of autonomic dysreflexia (A.D.). Forty-eight per cent of 213 patients with complete cord lesions at T6 or above exhibited A.D. The time of onset post-injury, exciting causes, unusual manifestations of attacks, and the persistence of the condition were studied. These findings and the experience with attempts at prevention by education and by the use of an alpha-adrenergic blocker and a non-adrenergic vasodilating agent are reported.