Despite longstanding beliefs, early repolarization is not always a benign electrocardiographic observation. Its association with increased arrhythmic events has been observed in 2 strikingly different groups of individuals, retrospectively in young subjects with idiopathic ventricular fibrillation and in long-term cohort studies from the general population. This form of primary electrical disease is now referred to as the early repolarization syndrome and has mechanistically been demonstrated to occur secondary to a transmural gradient of early cellular repolarization, resulting in the presence of an ST-elevation pattern and J-waves merged within or offset from the terminal QRS complex. In addition to creating a milieu of increased arrhythmic risk in isolation, an increasing number of studies have highlighted that the presence of early repolarization and J-waves may provide a baseline electrical substrate that modifies the risk of malignant arrhythmias in other clinical settings, such as acute myocardial ischemia. The challenge ahead lies in discerning when early repolarization may represent an ominous ECG marker, as opposed to a benign entity.