Over the past two decades there have been dramatic changes in the diagnosis, treatment and prognosis of acute coronary syndrome (ACS). Several new treatment modalities have been added and the prognosis has improved dramatically. Biomarkers play a crucial role in the management of ACS. At present, cardiac troponin is the biomarker of choice for diagnosis of acute myocardial infarction (AMI). Currently, there are no other biomarkers, which can compete, neither regarding specificity nor regarding early sensitivity. However, there is still a clinical need of a biomarker able to reliably rule-in or rule-out AMI immediately on admission. MicroRNAs seem to be promising new candidates for diagnostic purposes. The optimal combination of biomarkers and new imaging techniques is another important area for research. The list of biomarkers associated with an adverse prognosis in ACS is long. However, for most of them it has been very difficult to prove an added clinical value. Only cardiac troponin, and to some degree also B-type natriuretic peptides, is widely used in clinical practice for risk assessment. Among new markers, growth differentiation factor 15 and the midregional part of the prohormone of adrenomedullin, have shown some promising results. Since the renal function is assessed in clinical routine, also markers of the renal function have gained increasing interest. Cardiac troponin has been proven useful for selection of antithrombotic, antiplatelet and invasive treatment. Besides cardiac troponin, no other markers have consistently been shown to be useful for selection of specific treatments.