Recurrent syncope, malignant ventricular arrhythmias, and sudden death are complications of the long QT syndrome (LQTS), Two well-known syndromes with long QT intervals are known. The Jervell and Lange-Nielsen syndrome (JLNS) is characterized by prolongation of the QT interval, deafness, and autosomal-recessive inheritance, and the Romano-Ward syndrome is characterized by a prolonged QT interval, autosomal-dominant inheritance, and no deafness. In the present study assessment was performed of the diagnostic importance of the ventricular derepolarization parameters, clinical features, and prevalence of JLNS among 132 children with congenital hearing loss (CHL), In the CHL group the mean QT, QTc, JT, and JTc intervals and the dispersion values (QT-d, JT-d, QTc-d, and JTc-d) were significantly longer than those of control subjects (n = 96) (P < 0.05). Patients with CHL and JLNS (n = 5) had significantly longer mean values of QT, QTc, JT, and JTc intervals and dispersion values than those of CHL without JLNS (n = 127) and control subjects (P < 0.05). The results suggest that assessment of ventricular derepolarization parameters in children with CHL will be helpful in the early detection of JLNS because infants with CHL cannot accurately describe the symptoms of syncope, (C) 1999 by Elsevier Science Inc. All rights reserved.