The prognostic significance of preoperative atrial fibrillation (AF) at the time of aortic valve replacement is unknown, as is the potential role for concomitant arrhythmia surgery. We performed a cohort comparison of patients with preoperative AF (n = 129) and preoperative sinus rhythm (SR, n = 252) undergoing aortic valve surgery between 1993 and 2002; patients were matched for age, gender, and left ventricular ejection fraction. Follow-up (mean interval, 4.5 years) was 98% complete. Primary endpoints were late cardiac and all-cause mortality, as well as major adverse cardiac or cerebrovascular event. Patients with preoperative AF presented with more severe congestive heart failure (p = 0.03) and more often had significant tricuspid regurgitation (p = 0.01) preoperatively. They also had worse late survival (risk ratio [RR] for death = 1.5, p = 0.03) with 1-, 5-, and 7-year survival rates substantially reduced at 94%, 87%, and 50%, respectively, for those in AF versus 98%, 90%, and 61% for patients in sinus rhythm preoperatively. Individuals in AF had a greater probability of subsequent rhythm-related intervention (RR = 4.7, p = 0.0002), and more frequently developed congestive heart failure (25% vs 10%, p = 0.005) and stroke (16% vs 5%, p = 0.005). By multivariable analysis, preoperative AF was an independent predictor of late adverse cardiac and cerebrovascular events, but not late death. Performance of concomitant arrhythmia surgery in patients undergoing aortic valve surgery may reduce late morbidity; however, its potential impact on late mortality in this high-risk subset of patients remains unclear.