There are relatively few reported studies of continuous electrocardiographic recordings by the Holter method in children. We report our experience of 296 24-hour recordings in 160 patients (average age 10.5 years), investigated for suspected or known cardiac arrhythmias. One hundred and ten patients (68.75%) had no organic heart disease and 6 patients (3.75%) had acquired lesions. Eighty-three patients (52%) were symptomatic. Sixty-three patients (39%) had normal recordings; 97 patients (61%) had a total of 126 arrhythmias. There were 45 cases of atrioventricular block, 24 cases of sinus node dysfunction, 39 cases of supraventricular arrhythmias and 18 cases of ventricular arrhythmias. Overall, 47.6% of these rhythm disturbances were diagnosed by Holter monitoring. This technique was particularly valuable in the diagnosis of arrhythmias in symptomatic patients, patients with arrhythmogenic cardiac lesions and in the detection and surveillance of postoperative arrhythmias in congenital heart disease, of pacemakers, of congenital atrioventricular block and of the chronic arrhythmias of childhood.