Patients undergoing cardioversion for chronic atrial fibrillation should receive anticoagulation for three weeks before and four weeks after the procedure. Patients with atrial flutter and acute atrial fibrillation are also at risk of thromboembolic complications, so they too should be anticoagulated for cardioversion. Of the 36 acutely admitted patients who were cardioverted, 18 were in atrial fibrillation and 18 in atrial flutter. All except three of those in fibrillation were anticoagulated with heparin before cardioversion, but only seven received warfarin after cardioversion. Of those in flutter, 10 received heparin and eight received no anticoagulation before cardioversion. One patient underwent transoesophageal echocardiography before cardioversion to exclude atrial thrombi. Only two patients received warfarin for a month after cardioversion. Of the 20 elective cardioversions, 10 were in atrial fibrillation and 10 in atrial flutter. Five of those in fibrillation had received at least three weeks' treatment with warfarin before cardioversion and two underwent transoesophageal echocardiography; the other three received either up to two hours of heparin or no anticoagulation before cardioversion. Only five patients received warfarin for a month after cardioversion. Nine of those in flutter received a few hours of heparin before cardioversion and one was not anticoagulated; none underwent transoesophageal echocardiography or received warfarin after cardioversion. The results of this audit demonstrate that anticoagulation for atrial arrhythmias was inconsistent and often inadequate. A formal anticoagulation policy for cardioversion has now been adopted.