Cardiac mapping during sinus rhythm and during spontaneous or induced ventricular arrhythmias is a promising technique that offers a variety of potential strategies to improve our ability to locate abnormal areas in the heart that are the seat of arrhythmias. If surgical procedures are to become more limited in scope in an attempt to salvage myocardium, mapping will need to be used to a greater extent. However, it remains to be established which mapping technique will prove most sensitive and specific in detecting sites of arrhythmia, and whether the localizing method used allows a more directed surgical intervention to be successful.