The need for prophylactic anticoagulation before electrical cardioversion for atrial arrhythmias is clearly established in the case of atrial fibrillation. By contrast, such prophylaxis is not a current standard of care before cardioversion for pure atrial flutter, since this arrhythmia seems not to increase the risk of postcardioversion embolism. We present a patient who developed two cerebral embolisms 24 h after electrical cardioversion for pure atrial flutter. To our knowledge, this observation has not been previously reported.