Ventricular arrhythmias are often precipitated by physical or emotional stress, in particular in patients with ischemic heart disease or hereditary long QT syndrome. Stimulation of the sympathetic nervous system in response to exercise or emotional stress causes activation of cardiac α- and β-adrenoceptors. The rapid component of the delayed rectifier potassium current, IKr, and the underlying hERG potassium channel are critical for the regulation of heart rhythm. Recent experimental studies revealed that hERG/IKr currents are modulated by α- and β-adrenergic stimulation, providing a pathophysiological explanation for the increased incidence of arrhythmias during stress. This review summarizes the current knowledge on hERG/IKr channel modulation by adrenergic activity. In addition, therapeutic approaches to future effective, more genotype-specific antiarrhythmic therapies are discussed.