Diagnosis and risk stratification of patients with acute coronary syndromes remain extremely important in order to avoid unnecessary hospitalizations on the one hand, and to improve prognosis of these patients on the other. For diagnosis of acute coronary syndromes, an ECG should be obtained at rest, troponin T and I should be measured on admission and again 6 to 12 h later, and myoglobin or CK-MB should be determined in patients with recent syndromes and those with recurring ischemia. Risk should be assessed upon admission and repeatedly during the hospital stay. Early risk indicators are: age, mate sex, previous manifestation of coronary artery disease, history of left ventricular dysfunction or congestive heart failure and ongoing chest pain, as well as ST depression, transient ST segment elevation, and elevated levels of troponin T or I. Longer term risk assessment in unstable coronary artery disease includes rest and stress echocardiography, exercise ECG, thallium scintigraphy, as well as coronary angiography and left ventriculography. Markers of high long-term risk are old age, prior history of myocardial infarction, diabetes, elevated levels of C-reactive protein, and the extent of coronary artery disease and left ventricular dysfunction. (C) 2001 Elsevier Science Ltd. All rights reserved.