A 50-year-old man presented with palpitations. An ECG showed atrial flutter with a ventricular rate of 107 beats per minute and variable atrioventricular block. The QRS complex was normal in axis and duration with no signs of bundle branch block, ventricular hypertrophy, or prior myocardial infarction. The T waves were normal except in inferior leads and V6 where the saw-tooth pattern of atrial flutter made assessment difficult. The final diagnosis was atrial flutter with variable atrioventricular block and a ventricular rate of 107 beats per minute.