Patients with either unstable angina or non-ST-elevation myocardial infarction are usually submitted to the emergency department with similar symptoms and signs. Generally cardiac enzyme determinations can differentiate these two conditions. Elevation of these enzymes and their detection in blood stream takes a certain amount of time. A number of studies demonstrated lately that the high risk patients benefit more aggressive treatment modalities. Risk stratification and identification of the high risk patients became an essential part of the evaluation in emergency departments.