Background Atrial fibrillation (AF) occurs commonly in patients with acute myocardial infarction (MI) and is associated with an increased long-term mortality.This study aimed to investigate the clinical characteristics and outcomes of AF in in-hospital elderly Chinese patients with acute MI.Methods A total of 967 patients with acute MI,aged≥65 years,were categorized on the basis of the absence or presence of AF.Patients with documented AF were classified into two subgroups: the ongoing AF group and the new-onset AF group.We retrospectively evaluated the clinical profile,in-hospital outcomes,and effects of revascularization on the incidence of AF in elderly patients with acute MI.Results AF was documented in 100 (11.53%) patients and the incidence of new-onset AF was 6.51% during hospitalization.History of old MI and cerebrovascular events were more common in patients with AF than in those without AF (P