Several case reports have documented coronary artery stenosis or even occlusion after radiofrequency energy ablation (RFA) in children and adults. Coronary involvement early and late after RFA has also been described in animal models. The purpose of this study was to assess prospectively the incidence of coronary artery injury early after catheter ablation for supraventricular tachycardias (SVT) in children. From October 2002 to January 2008, 212 consecutive patients younger than 21 years with SVT underwent selective coronary angiography before and 30 minutes after RFA or cryoablation. Median patient age was 12 years (range 0.3-20.4 years), and median body weight was 47 kg (range 5.5-130 kg). An accessory pathway was diagnosed in 112 patients, AV nodal reentrant tachycardia (AVNRT) in 84 patients, and both an accessory pathway and AVNRT in 16 patients. Congenital heart disease was present in 31 patients. In 2 of 117 patients who had RFA for an accessory pathway, an acute reduction in luminal diameter of the coronary artery adjacent to the ablation site was observed. These two patients with a structurally normal heart showed ST-segment changes with normalization of the ECG within 1 week. Both were clinically asymptomatic, and two-dimensional echocardiography documented normal ventricular function. Noninvasive testing did not reveal any evidence of persistent myocardial ischemia. No coronary artery damage was noted after ablation for AVNRT or after ablation with cryoenergy. Coronary artery narrowing adjacent to the RFA site was noted in 2 of 117 patients with an accessory pathway and occurred only in patients with a posteroseptal pathway. Coronary angiography could be helpful in avoiding coronary lesions in these settings.