Shortly after in the introduction of programmed electrical stimulation (PES) of the heart to study and localize cardiac arrhythmias in the intact human heart, the technique was used for risk stratification of the arrhythmia patient. Two decades later we have to conclude that especially in ventricular arrhythmias the technique of PES did not live up to our expectations and the left ventricular function is a better long-term predictor than the induction of ventricular arrhythmias or the ability to find an antiarrhythmic drug able to prevent the initiation of the classically documented ventricular arrhythmia. Another sobering finding came from the analysis of the characteristics of the patient dying suddenly out-of-hospital, which showed that most of those patients could not be classified before the event as being at high risk using noninvasive or invasive testing, not even in those with a previous cardiac history. Monomorphic action potential (MAP) recordings have been of importance in our understanding of torsade de pointe arrhythmias in congenital and acquired QT prolongation. A major problem in case of a less generalized electrophysiological abnormality is the identification of the appropriate place where to put the MAP-electrode.