Animal models of myocardial ischemia have demonstrated reduction in arrhythmias using statins. It was hypothesized that previous statin therapy before hospitalization might be associated with reductions of in-hospital arrhythmic events in patients with acute coronary syndromes. In this multinational, prospective, observational study (the Global Registry of Acute Coronary Events [GRACE]), data from 64,679 patients hospitalized for suspected acute coronary syndromes (from 1999 to 2007) were analyzed. The primary outcome of interest was in-hospital arrhythmic events in previous statin users compared with nonusers. The 2 primary end points were atrial fibrillation and the composite end point of ventricular tachycardia, ventricular fibrillation, and/or cardiac arrest. In-hospital death was also examined. Of the 64,679 patients, 17,636 (27%) had received previous statin therapy. Those taking statins had higher crude rates of histories of angina (69% vs 46%), diabetes (34% vs 22%), heart failure (15% vs 8.4%), hypertension (74% vs 58%), atrial fibrillation (9.3% vs 7.0%), and dyslipidemia (85% vs 35%). Patients previously taking statins were less likely to have in-hospital arrhythmias. In propensity-adjusted multivariable models, previous statin use was associated with a lower risk for ventricular tachycardia, ventricular fibrillation, or cardiac arrest (odds ratio 0.81, 95% confidence interval 0.72 to 0.96, p = 0.002); atrial fibrillation (odds ratio 0.81, 95% confidence interval 0.73 to 0.89, p <0.0001); and death (odds ratio 0.82, 95% confidence interval 0.70 to 0.95, p = 0.010). In conclusion, patients previously taking statins had a lower incidence of in-hospital arrhythmic events after acute coronary syndrome than those not previously taking statins. Our study suggests another possible benefit from appropriate primary and secondary prevention therapy with statins.