Limited data are available on the electrocardiogram and ambulatory electrocardiogram recording (Holter) in children infected with the human immunodeficiency virus type 1 (HIV-1). The purpose of this study was to estimate the prevalence and cumulative incidence of rhythm and conduction abnormalities in HIV-1-infected children. Electrocardiograms and Holter monitoring studies were performed annually on 205 HIV-1-infected children enrolled after 28 days of life (group I), 93 HIV-1-infected infants enrolled during pregnancy or during the first 28 days of life (group IIa), and 463 HIV-1-uninfected infants enrolled during pregnancy or during the first 28 days of life (group IIb). The 5-year cumulative incidence in the group I children of second-degree atrioventricular block or supraventricular or ventricular tachycardia was 13.4%, and the 5-year incidence was higher for the older infected group I children (16.8% for children > or =4 years old at first study and 11.4% for children <4 years, p = 0.04). The mean corrected QT interval was also longer for the older infected group I children (p = 0.002) and prolonged in the HIV-1-infected compared to the HIV-1-uninfected group II children (p = 0.02). None of the children had atrial fibrillation or flutter. Arrhythmias are uncommon in children infected with HIV-1 and in children of HIV-1-infected mothers and the arrhythmias identified tend to be benign. Therefore, routine Holter monitoring does not appear to be indicated in asymptomatic children.