Objective: New-onset atrial fibrillation (AF) is the most frequent arrhythmic complication after coronary artery bypass grafting (CABG). Elderly patients who undergo this operation may have a different risk profile from the general population. The aim of this study was to identify risk factors for post-CABG AF in the elderly population. Methods: Between September 2001 and December 2005, 426 elderly patients (age 65 years) underwent CABG at our center. Ninety-one developed post-CABG AF (AF group), and the other 335 (no-AF group) did not develop this complication. Multivariate analysis (odds ratio, +/- 95% Cl, p value) was used to identify independent clinical predictors of post-CABG AF. Results: The incidence of post-CABG AF in elderly patients during the study period was 21.4%. Multivariate analysis identified age (OR 1.07, p < 0.009), age >= 75 years (OR 1.77, p < 0.042), preoperative renal insufficiency (OR 5.09, p < 0.035), EuroSCORE (OR 1.18, p < 0.038), and cross-clamping time (OR 1.02, p < 0.012) as predictors of AF occurrence. The AF group had a significantly longer mean intensive care unit (ICU) stay (3.8 +/- 4.7 vs. 2.5 +/- 1.3 days for AF vs. no-AF; p = 0.0001), and a significantly higher proportion of patients with prolonged ( >= 6 days) ICU stays (8.8% vs. 3.2%, respectively; p=0.033). Hospital mortality was 3.2% in the no-AF group and 2.2% in the AF group (p = 0.74). Conclusion: This study of elderly patients reveals some novel predictors of post-CABG AF, most notably preoperative renal insufficiency and EuroSCORE. It is important to identify risk factors for post-CABG AF in all patient groups as this knowledge might lead to better prevention of this problem and its potential consequences.