Methemoglobin forming agents are widespread in medical substances and in natural environment. Moreover methemoglobin is continously produced in human erythrocyte but its concentration is kept low (1-2%) by special enzymatic configurations. Toxic methemoglobinemia is caused by extensive oxydation of ferrous iron within the hemoglobin molecule which leads to tissue hypoxia. A case of 74 old man referred to the SOR SPSK AMB because of an unknown substance and alcohol poisoning is analyzed in this paper. The general condition of the patient was very serious, he remainded unconscious, with respiratory and cardiovascular inefficiency and cyanosis. Methemoglobin concentration was 65,5% of total hemoglobin. Alredy during the first 24 hours of hospitalization the condition of the patient improved significantly (decrease of the methemoglobin concentration and increase of circulatory system function). In the next 24 hours changes in the electrocardiography were noticed, suggested acute coronary syndrome. It was confirmed by increase in Troponin I concentration up to 5,34 ng/ml The changes suggested non ST elevation myocardial infarction. During the hospitalization the troponin I concentration gradually decreased to 2,7 ng/ ml. On the 4th day of hospitalization the condition of the patient was good and he was admitted to Department of Cardiology.