The purpose of this study was to investigate the association of atrial fibrillation (AFIB) with multiple measures of cognitive performance in a large community-based sample extensively characterized for vascular risk factors. Our primary analysis included 1011 Framingham Offspring Study (Framingham, Mass) men, mean age = 61.0 (37-89) years, free of clinical stroke and dementia. Using multivariable linear regression models, we related the presence (n = 59) versus absence (n = 952) of AFIB in men to a global measure of performance and multiple measures of specific cognitive abilities assessed an average of 8 months after the AFIB surveillance period. Adjusting for age, education, multiple cardiovascular risk factors, and cardiovascular disease, men with AFIB exhibited significantly lower mean levels of cognitive performance compared with men in normal sinus rhythm. Men with AFIB exhibited lower performance on global cognitive ability and cognitive abilities including Similarities (abstract reasoning), Visual Reproductions-Immediate Recall, Visual Reproductions-Delayed Recall, Visual Organization, Logical Memory-Delayed Recall, and Trail Making A (scanning and tracking) and Trail Making B (scanning, tracking, and executive functioning). Further studies leading to a better understanding of the mechanisms underlying the relation between AFIB and cognitive performance are important.