The effect of statins on the incidence of new-onset atrial fibrillation (AF) in patients presenting with suspicion of acute coronary syndrome (ACS) is unknown. Our study population consisted of patients admitted to a tertiary care Veterans Administration hospital with suspicion of ACS between November 2001 and January 2006. All patients had an electrocardiogram on admission that was compared with a previous electrocardiogram to confirm new-onset AF or atrial flutter. Of 1,526 patients, 164 (10.8%) had new-onset AF and 601 (39.4%) were on a statin on admission. Patients with AF were significantly more likely to be older, Caucasian, have renal insufficiency and anemia, and less likely to be diabetic, on a statin or angiotensin-converting enzyme inhibitor on admission, or have chest pain as a presenting complaint. In univariate analysis, patients on statins were significantly less likely to have new-onset AF (odds ratio 0.40, 95% confidence interval 0.33 to 0.69, p <0.01). This relation persisted in the multivariate model (odds ratio 0.57, 95% confidence interval 0.39 to 0.83, p <0.01) after correcting for age, race, diabetes mellitus, chest pain, and use of angiotensin-converting enzyme inhibitor. In conclusion, patients presenting with suspicion of ACS were much less likely to have newonset AF if they were on a statin at time of presentation.