In athletes, ventricular arrhythmias and sudden cardiac death are rare and unpredictable events. Often, an underlying heart disease is present, but pre-existing clinical signs or symptoms may not be recognized. Primary electrical disorders (such as the long QT syndrome) are rarely present in athletes but, so far, are a considerable reason for disqualification from sport activity. These disorders are mostly inherited, and patients should be referred to a cardiologist with special experience. Through the efforts of molecular genetics and cellular electrophysiology, an increasing understanding of the underlying mechanisms of arrhythmogenesis is being gathered. During the past decade, evidence has grown that establishing accurate genetic diagnoses and dissection of molecular disease mechanisms can have an impact on prognosis, and help direct therapy in a range of cardiovascular diseases. Further achievements in the areas of clinical and molecular research, improvement of medical education, and expansion of genotyping facilities will facilitate the correct and immediate identification of affected patients.