Tilt test for diagnosis of unexplained syncope in pediatric patients. Thirty-five teenage patients with a history of presyncope or syncope underwent a passive head-up tilting to reproduce symptoms of syncope. If tilting alone did not induce syncope, isoproterenol infusion was given to increase heart rate to 150 to 160 beats per minute. In 80% of patients with a history of syncope, identical symptoms could be reproduced during tilting: an abrupt fall in blood pressure combined with profound nodal bradycardia, ranging from 32 to 86 beats per minute. These symptoms were quickly reversed by returning the patient to the supine position. For patients with frequent occurrences of syncope, especially when there was a history of trauma sustained during these episodes, a therapeutic regimen of either beta blockers or 9 alpha-fluorocortisol was begun. The mechanisms of this common cause of syncope in childhood is neurocardiogenic in response to venous pooling and catecholamine-induced tachycardia. The tilt test is an excellent and cost-effective test for the workup of unexplained syncope in childhood. 