A 52 year old man was admitted to an emergency department with a fast ventricular rate atrial fibrillation after an electrical shock. Electrical cardioversion was attempted after echocardiographic examination. This failed, but the heart rate slowed. Successful pharmacological cardioversion was achieved after 16 hours of amiodarone infusion. Pre-excitation syndrome was detected on baseline echocardiograph. Serum cardiac specific markers were all within normal limits. No abnormal findings were detected by chest radiography, echocardiographic, or coronary angiographic investigations. Acute onset atrial fibrillation after electrical injury is discussed.