Arsenic intoxication is a common form of heavy metal poisoning. Although arsenic-induced circulatory collapse, seizures, and syncope are well known, the potential for serious ventricular arrhythmias is less well recognized. Reported in this study are two cases of arsenic poisoning causing torsade de pointes. Furthermore, marked prolongation of the QT-U interval and the rarely observed phenomenon of T-U wave alternans are demonstrated. Thus, arsenic intoxication may be complicated by prolongation of the QT-U interval and torsade de pointes. T-U wave alternans occurs in the presence of a long QT-U interval and may be an electrocardiographic warning sign of torsade de pointes.