A reasonably precise and mechanistic diagnosis of the cause of supraventricular tachycardia (SVT) can be made using noninvasive tests such as an electrocardiogram, Holter monitoring, or cardiac event recorder and by determining the response to vagal maneuvers (or intravenous adenosine). Therapy options include prophylactic drug therapy, catheter ablation, and doing nothing (for those with infrequent and non-life-threatening symptoms). Drug therapy attempts to suppress the arrhythmia rather than to cure it and could cause side effects. The success of pharmacologic treatment depends on patient compliance and is costlier than catheter ablation in the long run. Catheter ablation has a high success rate and low complication rate in patients with the common forms of SVT (Wolff-Parkinson-White syndrome, concealed accessory pathways, and atrioventricular nodal reentrant tachycardia ) and is the first choice therapy in children beyond 6 to 7 years of age. In younger patients (less than 5 years), although feasible, catheter ablation is reserved for patients with life-threatening arrhythmia or those failing drug therapy. There is a small risk of sudden death in patients with Wolff-Parkinson-White syndrome, whether symptomatic with SVT or not. Management of asymptomatic patients with Wolff-Parkinson-White syndrome is controversial. Noninvasive (Holter monitoring, exercise tests) and if necessary, invasive (electrophysiology study) assessment may help refine the risk for the individual patient.