Background: A quantitative history using Calgary syncope syndrome score (CSSS) is able to define the likely cause of syncope, but there is still a lack of diagnostic screening tests for vasovagal syncope (VVS). The aim of the present study was to develop a screening test for VVS on the basis of CSSS and the relationship between polymorphic variants of the G-system signaling protein genes and tilting results. Methods and Results: From 730 syncopal patients, 307 consecutive subjects without structural and electrical abnormalities were genotyped and examined on blood pressure (BP) and tilt testing. Genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism in genes encoding Gsα-protein GNAS1 (rs7121), G-protein β 3 subunit (rs5443) and the cardiac regulator of G-protein signaling RGS2 (rs4606). The control group consisted of 100 healthy volunteers with a negative history of syncope. From multivariate regression analysis, being a carrier of 393T GNAS1 (odds ratio [OR], 2.29) and systolic BP (OR, 0.98) remained as independent factors associated with positive tilt results. The resultant screening test for VVS consisted of the following: carrier of 393T GNAS1; systolic BP <131mmHg (from the receiver operating characteristic [ROC] curve); and CSSS ≥-2. Using ROC curve analysis for systolic BP and CSSS, 2 final models for the screening test were constructed: highest sensitivity (89%) and highest specificity (99%). Conclusions: The novel screening test including the variation of Gsα protein gene seems to be helpful to identify tilt-induced vasovagal patients. (Circ J 2011; 75: 2182-2186)