Ventricular preexcitation syndromes are important because they are associated with paroxysmal tachycardias that can result in serious cardiovascular complications and sudden death. These syndromes are also important because the ECG findings, if unrecognized, are frequently misdiagnosed as something else. With the use of "classic" syndrome names, for example, the Wolff-Parkinson-White (WPW) syndrome, physicians tend to think of ventricular preexcitation in a rigidly defined sense (short PR interval, delta wave, and abnormal QRS). A broader view of ventricular preexcitation allows one to think of it as an entity with endless variations. Failure to recognize the wide ECG variations in which ventricular preexcitation occurs may have substantial clinical consequences relative to misdiagnosis and treatment.