Sudden cardiac death (SCD) is usually the result of an interaction between transient acute events (’triggers’) and either structural or non-structural cardiovascular substrates. The structural culprit resides in any of the cardiovascular components, i.e. aorta, coronary arteries, myocardium, valves, conduction system, or ion channels. Epidemiological studies have demonstrated that the occurrence of SCD in athletes is nearly three times than that in non-athletes, so that sport activity adds a significant risk if the athletes are affected by concealed cardiac diseases. Triggers of SCD in young competitive athletes include exercise-related sympathetic stimulation, abrupt haemodynamic changes, and myocardial ischaemia. In this chapter, we will review the various structural diseases, either congenital or acquired, which pose a risk of SCD in athletes. Disparities among published studies emphasizes the need for uniform reporting (source of data, retrospective versus prospective, autopsy versus no autopsy, etc). Identifying causes of SCD in the athletic population is important for guiding preventive measures.