Background:Head-up tilt testing is a useful test for diagnosing syncope, but time-consuming procedure. Early heart rate(HR) increase was one of parameters to predict the result of tilt test. However there are still controversy about the predictive value of early HR increase during tilt test. The aim of this study was to investigate whether the early HR increase and other blood pressure(BP) parameters were correlated with the result of head-up tilt test. Methods:The study included 40 consecutive patients(mean age : 40.6 짹 13.9, 14 men, 26 women) with syncope, with stable sinus rhythm and without structural heart disease who were undergoing head up tilt test. To evaluate the effect of BP change on the result, patients who take anti-hypertensive medications were excluded. A two-phase 20-minutes tilt table test (70째 angle) was performed. The initial phase was passive, and the second phase required isosorbide dinitrate 1-puff(1.25mg)inhalation. The HR increment and BP changes induced by the tilt maneuver and by the isosorbide dinitrate inhalation were analyzed. The early HR increase was defined as the maximum HR during the first 6-minutes of tilting minus the resting HR in supine position. Rate of early HR increment was calculated as early HR increase /supine HR x 100(%). Results: Twenty nine patients(73%) had a positive tilt test, and 11 patients(27%) had a negative test. Four patients(14%) had positive response at passive phase and twenty five patients(86%) had positive response after isosorbide dinitrate inhalation. The mean BP at supine and erect position were lower in tilt positive group than in tilt negative group (98.8짹10.4mmHg vs 117.1짹14.3mmHg in supine position, 100.4짹11.6mmHg vs 116.8짹14.2mmHg in erect position). Early HR increase was not statistically different in tilt positive group from in tilt negative group(15.75 짹 7.91 beats vs 10.64 짹7.68 beats, P=0.075). However the rate of increment of HR during first 6 minutes was significantly higher in tilt positive group than in tilt negative group (25.43짹13.92 % vs 10.64짹7.68 % , P=0.036). Conclusion : Rate of HR increment during 6 minutes may be used for predicting the result of tilt test for syncope patients.