The acute coronary syndromes without ST elevation (NSTEMI-ACS) include unstable angina (UA) and myocardial infarction without ST segment elevation (NSTEMI). The estimated incidence of hospital admissions for NSTE-ACS is about 3/1000/year. Both clinical manifestations of ischemia as well as increased markers of myocardial necrosis (troponin T or I) are needed for correct diagnosis of NSTEMI. Diagnosis of NSTEMI is influenced by clinical manifestation of the disease and sensitivity of biomarkers. However, troponin can be elevated in the absence of myocardial infarction as well. There is necessary to search for other causes of increased troponin in the absence of ischemic symptoms. Although not beeing diagnosed with myocardial infarction, elevated troponin indicates a poorer prognosis in these patients. These facts have to be considered before rational indication of troponin level assessment.