Left arm and left leg lead reversal is difficult to recognize without a prior comparative ECG. Left arm and left leg lead reversal on an ECG did not affect quality of care in this series of 58 cases of lead reversal. Lead reversal may be due to improper location of the leads at the cable junction of the ECG machine itself. Standardization of education for performance of ECGs as well as standardization of machine maintenance checks should decrease this type of medical error.