Over the past half century, LQTS has matriculated through several critical milestones including its sentinel clinical description, clinical diagnostic scorecard, pathogenetic discovery, decade of research-based genetic testing and genotype–phenotype correlations, and clinical availability of genetic testing. In this chapter, we will discuss the history, epidemiology, and clinical presentations of congenital long QT syndrome (LQTS). We will clarify current diagnostic approaches to LQTS, including clinical history and specific diagnostic testing. Treatment strategies including pharmacologic and surgical techniques will be examined, as well as the role of individualized treatment for the LQTS patient. Finally, preventative strategies will be discussed, including athletic participation.