To identify high-risk patients with Brugada syndrome, the present study reviewed 60 standard 12-lead electrocardiograms from 60 patients collected by the Japanese Brugada syndrome registry. Under blinded conditions, the S wave of lead V(1) was measured from the tip of r to r', and the amplitude of the ST segment in lead V(2) was measured at 0.08 s from the J point. In patients with ventricular fibrillation (n=17), the S wave was significantly longer in V(1) (0.085+/-0.007 s vs 0.075+/-0.011 s, p=0.001), and ST segment elevation in V(2) was significantly greater (0.323+/-0.133 mV vs 0.236+/-0.129 mV, p=0.012) than in patients without fibrillation. An S wave width of 0.08 s or more in V(1) had a positive predictive value of 40.5% and negative predictive value of 100% for ventricular fibrillation, with 100% sensitivity. ST elevation of 0.18 mV or more in V(2) had a positive predictive value of 37.8% and a negative predictive value of 100% for ventricular fibrillation, with 100% sensitivity. Both an S wave width > or =0.08 s in V(1) and ST elevation > or =0.18 mV in V(2) were highly specific indicators of ventricular fibrillation and are proposed as new criteria for high-risk Brugada syndrome.