Aims Previous studies have suggested that upstream medical therapy to modulate the renin-angiotensin axis may facilitate left atrial remodelling and thereby prevent new-onset atrial fibrillation (AF). The purpose of this study was to evaluate the association between angiotensin converting enzyme inhibitor (ACEI) and angiotensin receptor blockers (ARB) on new-onset AF in a large cohort of patients with coronary artery disease (CAD).Methods and results This was a population-based study of 28 620 patients, from community-dwelling Medicare beneficiaries who had been hospitalized for acute myocardial infarction or coronary revascularization (1995‚Äì2004). All patients, 65 years and older, had a mean follow-up period of upto 3.8 ¬± 3.0 years. Patients with a history of AF before and during hospitalization were excluded. ¬†We compared the incidence of new-onset AF between patients who were (N= 10 918) and were not (N= 17 702) prescribed ACEI and/or ARB within 1 month of hospital discharge following cardiac event. New-onset AF within 5 and 10 years was 39.1 and 61.1%, respectively, in patients who received ACEI/ARB, compared¬† 34.9 and 53.6% in patients who did not receive them [unadjusted hazard ratio (HR): 1.16; 95% confidence interval (CI): 1.11, 1.21]. Multivariable analysis adjusting for patient- and hospital-related characteristics indicated that ACEI/ARB use independently had no impact on the risk of developing new-onset AF compared with non-users (adjusted HR: 0.99; 95% CI: 0.94, 1.04). Adjustment for propensity-score and health-seeking behaviours yielded nearly identical results.Conclusion Angiotensin converting enzyme inhibitor/ARB therapy initiated within 1 month after hospital discharge is not associated with a reduction in the risk of new-onset AF after myocardial infarction or coronary revascularization.