In Italy the existence of a law on health protection of competitive sports since 1982 has favored the creation and the revision of these cardiological guidelines (called COCIS), which have reached their fourth edition (1989-2009). The present article is the second English version, which has summarized the larger version in Italian. The experience of the experts consulted in the course of these past 20 years has facilitated the application and the compatibility of issues related to clinical cardiology to the sports medicine field. Such prolonged experience has allowed the clinical cardiologist to acquire knowledge of the applied physiology of exercise and, on the other hand, has improved the ability of sports physicians in cardiological diagnostics. All this work has produced these guidelines related to the judgment of eligibility for competitive sports in the individual clinical situations and in the different cardiovascular abnormalities and/or heart disease. Numerous arguments are debated, such as interpretation of the athlete's ECG, the utility of a preparticipation screening, arrhythmias, congenital heart disease, cardiomyopathies, arterial hypertension, ischemic heart disease and other particular issues.