Heart tumors in children are rare. Though of benign pathology they are clinically malignant and should be diagnosed early and promptly treated by surgery in spite of the poor results usually obtained. Any heart enlargement in the absence of congenital heart disease accompanied by rhythm and conduction troubles must be considered as suspect. Five cases of heart tumor are reported and clinically described. Four occurred in newborns and the remaining one before the age of one. Heart enlargement was a constant finding. The ECG findings were: W.P.W. syndrome, intraventricular conduction troubles and ventricular tachycardia, wandering pacemaker (one case each) and ventricular hypertrophy with surprisingly low voltages in the corresponding chest leads (two cases).