Apparent life-threatening event (ALTE) is a term used to define an event of unknown cause after an infant is found limp, cyanotic, bradycardic, and/or requires resuscitation. Eight to 15% of children with ALTE die of sudden infant death syndrome. Obstructive sleep apnea, bradycardia, gastroesophageal reflux, and laryngotracheal abnormalities are frequently associated with ALTE. Wide QT dispersion is associated with sudden death in heart failure and increased risk of ventricular fibrillation in acute myocardial infarction. Here, we assess QT dispersion in infants with ALTE and its correlation to clinical and electrocardiographic indices. The study included eighty nine infants (age 2.14 +/- 1.8 months, 46 males and 43 females) referred with ALTE to the pediatric emergency room and 18 controls (age 2.77 +/- 2.2 months) who underwent electrocardiogram assessment of QTmin, QTmax, QT dispersion (QT-D), and as well as QTmin, QTmax, and QT-D corrected for heart rate (QTcmin, QTcmax, QTC-D, respectively). All infants were referred at the usual diagnostic tests-the gastroesophageal reflux test, apnea monitoring, Holter ECG monitoring, electroencephalogram, and Doppler echocardiography. QT-D, QTc-D, and QTc-min were significantly greater in the ALTE group (p < 0.01). Greater QTc-D was found in males compared to females (p < 0.001). QT-D and QTc-D showed little or no correlation with age of infant or positivity of diagnostic tests. QTc has been found by multiple regression analysis to be the independent variable with the greatest impact on QTc-D (beta = -0.68, p < 0.001).