The treatment of arrhythmias during pregnancy is complicated by concerns for fetal well-being. Although no drug is absolutely safe, most are well tolerated. Nonpharmacologic therapy includes vagal maneuvers and esophageal pacing. Temporary and permanent pacing have been used safely during pregnancy, as has direct current cardioversion. Cardiopulmonary resuscitation is complicated by concerns for the fetus, which may be viable at 25 weeks. Diagnosis of the cause of tachyarrhythmias may be enhanced by roving chest leads or esophageal recording. Both supraventricular and ventricular tachycardias may become manifest during pregnancy, and conservative management is desirable if the symptoms are mild. Supraventricular tachycardias respond acutely to adenosine. Ventricular arrhythmias during pregnancy often occur in the absence of structural heart disease and are responsive to drug therapy. The safe use of an implantable cardioverter-defibrillator has been described.