Molecular genetic studies in the last 2 decades have revealed a link between several inherited cardiac arrhythmias and genes encoding for ion channels or other membrane components. Two recent international expert consensus statements endorsed by 3 continental electrophysiology societies have updated the clinical and genetic diagnoses and management in patients with inherited arrhythmia syndromes, including congenital long QT syndrome (LQTS) and Brugada syndrome. Thirteen genotypes have been identified in 50% to 80% of clinically affected patients with congenital LQTS. Therefore, genotype-phenotype correlations have been investigated, especially, in the 3 major genotypes-LQT1, LQT2 and LQT3 syndromes-enabling genotype-specific management and therapy. On the other hand, less than half of patients with Brugada syndrome can be genotyped, and mainly for the sodium channel gene, SCN5A. However, recent advances in molecular genetic testing include genome-wide association studies using gene arrays and targeted, whole-exome and whole-genome next-generation sequencing techniques. In this article, I will review the clinical and genetic diagnoses in congenital LQTS and Brugada syndrome.