To determine (a) the age distribution at first clinical supraventricular tachycardia (SVT) presentation; (b) the time interval between first clinical suspicion and electrocardiographic proof of SVT; c) the most indicative symptoms and signs of SVT; and (d) the SVT mechanism and its age distribution according to surface ECG. The records of 55 children (32 males and 23 females) with electrocardiographically proven SVT but without congenital heart disease were reviewed. At diagnosis, 27 patients (49%) were younger than 1 y (infants), and 28 (51%) were older than 1 y (children). Only a quarter of infants presented with symptoms. The majority (20/27), however, were detected during routine investigation without having any complaints. Children presented with symptoms (mostly palpitations) in almost 90% of cases. Despite these symptoms, the median time interval between first clinical presentation suggestive of SVT and electrocardiographic proof of SVT was 138 d. Using surface ECG, we were unable to show any age-dependency of the SVT mechanism in our study group. In infants SVT is a chance finding; SVT can only be proven electrocardiographically with a median delay of 138 d, despite the presence of symptoms; SVT using a (concealed) accessory pathway is the most common mechanism.