Myoglobin is a small heme-containing protein (153 amino acid residues, molecular weight (w/o heme) 17053 Da and theoretical pI=7.29), that is responsible for the oxygen deposition in muscle tissues. Only one form of myoglobin is expressed in cardiac. Myoglobin is known as a marker of myocardial damage and it has been used for more than three decades. Nowadays, it continues to be is very commonly used in clinical practice as an early marker of AMI. It appears in patients’ blood 1 – 3 hours following onset of the symptoms, reaching peak level within 8 – 12 hours. Myoglobin is not so cardiac specific as cTnI or cTnT. Due to high myoglobin concentration in skeletal muscle tissue, even minor skeletal muscle injury results in the significant increase of myoglobin concentration in blood. Therefore, myoglobin is used together with cTnI or cTnT in clinical practice for improved specificity in AMI diagnosis.