In patients with acute coronary syndromes cardiac troponins are sensitive markers of myocardial damage. The troponin complex comprises subunits C, T and I and is a major component in the process of myocyte contraction and relaxation. The T and I subunits have cardiac isoforms with distinct specific immunologic properties which distinguish them from similar subunits of non-cardiac muscle tissue. The high sensitivity and specificity of cardiac troponins make them the preferred biochemical markers for diagnosing acute myocardial infarction and for the triage of patients admitted with chest pain without ST segment elevation on the E.K.G. There is a correlation between cardiac troponin levels and prognosis in patients with acute coronary syndromes. In addition to their prognostic role, cardiac troponins play a role in selecting patients for contemporary treatments. Thus, their level can identify the patients most likely to benefit from treatments such as low molecular-weight heparin, IIb/IIIa receptor blockers and early angiography and coronary intervention. Recently, the American heart Association, the European Heart Society and the Israel Cardiology Society have published guidelines for the use of cardiac troponins. This review summarizes the current data regarding the use of cardiac troponins in the acute coronary syndromes.