Long QT syndrome(LQTS)is the prototype of the cardiac ion channelopathies,which cause syncope and sudden death.Inherited LQTS is represented by the autosomal dominant Romano-ward syndrome(RWS),which is not accompanied by congenital deafness,and the autosomal recessive Jervell and Lange-Nielsen syndrome(JLNS),which is accompanied by congenital deafness.The LQTS-causing mutations have been reported in patients and families from Europe,North America and Japan.Few genetic studies have been carried out in families with JLNS from China.This study investigates the molecular pathology in four families with LQTS(including a family with JLNS) in the Chinese population.Polymerase chain reaction and DNA sequencing were used to screen for KCNQ1,KCNH2,KCNE1,KCNE2 and SCN5A mutation.A missense mutation G314S in an RWS family was identified,and a single nucleotide polymorphism (SNP)G643S was indentified in the KCNQ1 of the JLNS family.In this JLNS family,another heterozygous novel mutation in exon 2a was found in KCNQ1 of the patients.Our data provide useful information for the identitication of polymorohisms and mutations related to LOTS and the Brugada Syndrome (BS)in Chinese populations.