Experience with oral sotalol, a beta-blocker with class III-antiarrhythmic properties, is limited in the pediatric population. Sotalol was administered to 32 patients with a mean age of 8.7 years (range 1 day-19.9 years). Mean dosage was 4.6 (1.5-9.4) mg/kg or 122.1 (52-306) mg/m2, respectively. In 27/32 patients, at least 1 antiarrhythmic agent had failed to control the dysrhythmia before sotalol was started. Cardiac diagnoses included normal heart (n = 16), status after correction of congenital heart disease (n = 13), and cardiomyopathy (n = 3). Success (based on symptoms and 24-h electrocardiogram) was achieved in 16/18 patients with reentry supraventricular tachycardia, in 7/8 patients with atrial flutter, and in 4/6 patients with ventricular tachycardia. During a mean follow-up of 15.6 (2-78) months, proarrhythmia occurred in five (16%) patients (symptomatic bradycardia n = 2, QT-prolongation and ventricular extrasystoles n = 1, ventricular extrasystoles n = 1, 2 degrees av-block n = 1), requiring dosage reduction (n = 3), cessation of treatment (n = 1) and pacemaker implantation in one patient, respectively. Symptomatic hypotension was noted in two patients, in whom therapy had to be stopped. Sotalol was a very effective agent for the treatment of various pediatric cardiac dysrhythmias. However, incidence of proarrhythmic effects warrants close electrocardiographic monitoring.