Long QT syndrome (LQTS) is a disorder of cardiac ion channels. Its importance lies in the potential for development of fatal arrhythmias on anaesthesizing undiagnosed patients. Pathophysiology of LQTS explains the molecular and cellular basis of the condition. Clinical picture and diagnosis of the disease are the first line of defense against undiagnosed patients. Better understanding of the effects of anaesthetic drugs is essential in order to improve anaesthetic management of the disease.