Sudden cardiac arrest is most often the first clinical manifestation of an 
underlying cardiovascular disease and usually occurs in previously asymptomatic 
athletes. The risk benefit ratio of physical exercise differs between young 
competitive athletes and middle-age/senior individuals engaged in leisure-time 
sports activity. Competitive sports are associated with an increase in the risk 
of sudden cardiovascular death (SCD) in susceptible adolescents and young adults 
with underlying cardiovascular disorders. In middle-age/older individuals, 
physical activity can be regarded as a 'two-edged sword': vigorous exertion 
increases the incidence of acute coronary events in those who did not exercise 
regularly, whereas habitual physical activity reduces the overall risk of 
myocardial infarction and SCD. Although cardiovascular pre-participation 
evaluation offers the potential to identify athletes with life-threatening 
cardiovascular abnormalities before onset of symptoms and may reduce their risk 
of SCD, there is a significant debate among cardiologists about efficacy, impact 
of false-positive results and cost-effectiveness of routine screening. This 
review presents an appraisal of the available data and criticisms concerning 
screening programmes aimed to prevent SCD of either young competitive athletes 
or older individuals engaged in leisure-time sports activity.