Seven out of 829 pediatric cardiac patients (0.84%) were found to have sinus node dysfunction (SND) over the past seven years. Of the seven patients, three had structurally normal hearts. One of these three patients had long QT syndrome. In four patients, structural heart disease was noted. In three of these four patients the sinus node dysfunction was attributed to cardiac surgery. The age of onset of SND ranged from four months to eight years. Presenting symptoms and signs included syncope, near-syncope, seizure and congestive heart failure. Two patients were asymptomatic. Five patients had episodic sinus pause. Sinus or junctional bradycardia was noted in four patients. Three had tachy-bradycardia. High grade atrioventricular block was noted in one patient. Treadmill exercise test revealed a nonsustained ventricular tachycardia in two patients. All seven patients were found to have prolonged maximal corrected sinus node recovery time. Prolonged intra-atrial conduction time was found in three, prolonged AV nodal conduction time in one, and prolonged His-Purkinje conduction time in one patient during the electrophysiologic study. All seven patients showed abnormal results in intrinsic heart rate study. Anti-arrhythmic drugs were prescribed. During the follow-up study, no patient died, but two patients received a pacemaker implantation. Because of the extent of their conduction system diseases, it is recommended that patients with SND should be thoroughly investigated.