Although the first gene responsible for long QT syndrome was described more than a decade ago, only now has the genetic testing become readily available to clinicians treating patients with inherited arrhythmia syndromes. Recognition of these syndromes, including long QT syndrome, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia, and arrhythmogenic right ventricular cardiomyopathy, is important for both internists and cardiologists. The potential for malignant ventricular arrhythmias and sudden cardiac death makes integration of clinical and genetic information critical for managing these patients. Although the presence of variable penetrance and genotype-phenotype correlations can limit the effectiveness of widespread genetic screening, directed genetic testing can be very helpful in confirming diagnosis, delineating prognosis, and identifying high-risk individuals.