Echocardiography provides a valuable tool for the evaluation and assessment of atrial function in patients with atrial fibrilation (AF). Atrial morphology after restoration of sinus rhythm is dynamic, with a decrease in atrial size if sinus rhythm is maintained and atrial growth among those with sustained AF. Restoration of electrocardiographic sinus rhythm is frequently accompanied by relatively depressed atrial mechanical function, with recovery that appears to be related to multiple factors, including the duration of AF before cardioversion and the mode of cardioversion. Such delay appears to confer ongoing risk for thrombus formation and thromboembolism in the days after cardioversion and argues strongly for the need to maintain therapeutic anticoagulation during the pericardioversion and postcardioversion period.