In adults, increased QT dispersion has been shown to predict arrhythmic risk as well as risk of sudden death in several clinical settings. It is controversial whether QT and JT dispersion are increased in children with ventricular ectopy and a structurally normal heart. We studied two groups of children: 25 patients with ventricular ectopy and 25 healthy children as controls. Standard electrocardiograms were reviewed and dispersions of both corrected QT (QTc) and JT (JTc) intervals were compared. We conclude that QTc and JTc dispersions are significantly increased in children with ventricular ectopy compared to control subjects.