Abstract: The purpose of the present study is to investigate the clinical usefulness of multi-stage headup tilt table test in patients with syncope of unexplained origin,Thirty-five patients（mean age 40±8years） with syncope of unknown origin and 20 patients（mean age 49±7years） with sinus bradycardia as controls were subjected to successive 80°headup tilt testing during infusions of 0,1,2 and 3μg/min of isoproterenol.The 28 of 35 patients with syncope of unknown origin who underwent the test developed presyncope or syncope（80%positive response）.Only 2/20 patients with sinus bradycardia developed syncope （10%positive re-sponse）.There was a highly significant statistical difference in positive response between two groups （P＜0.001）.In tilt table test isoproterenol （≤3μg/min）was required to produce positive response in ＞90%of posi-tive tests.A head-up tilt test lasting only 5 min is sufficient to induce positive response.The mean heart rate,mean blood pressure and rate-pressure product≥1.3 ×10￣3 kPa/min accurately identify both positive and nega-ive test results(positive predictive value≤1.2×10￣3 kPa/min regardless of testing time and isoproterenol dose,These results suggest that tilt table testing combined with isoproterenol infusion is a valuable provoca-tive tool for vasovagally mediated syncope.