Risk stratification for malignant arrhythmias and risk of sudden cardiac death in tetralogy of Fallot (TOF) remains challenging. We aimed to ascertain factors associated with life-threatening arrhythmic events. A multicenter retrospective case-control study including 72 TOF patients with documented cardiac arrest and/or sustained ventricular tachycardia, compared with 216 controls matched for era of surgery. The mean age at event in the cases was 27.3 ± 12.5 years. The majority (57%) presented with sustained ventricular tachycardia. Fatal events occurred in 9. Random forest analysis and a decision tree demonstrated surgical era specific risk factors (< vs ≥ 1980). For both eras, arrhythmic symptoms and left ventricular dysfunction were strongly associated with malignant arrhythmias. In addition, right ventricular dysfunction and age at repair ≥ 6.5 years preceded by a shunt were associated with a higher risk group in the early era, whereas a trans-annular patch type repair was associated with a lower risk group in the recent era. For the moderate and high-risk groups, the decision tree showed a sensitivity of 88.4% and specificity of 68.1%. An "importance factor" was calculated for each predictor, creating a risk score and 4 risk categories. In conclusions, this risk stratification scheme, based on clinical history and noninvasive testing, allows categorization of TOF patients at high risk of malignant arrhythmia. A multicenter prospective evaluation of the accuracy of this scoring system is now being planned.