The authors analyzed the cause of diagnostic errors due to incorrect ECG interpretation. It was revealed that the cause for diagnostic errors may lie in the inadequate experience of the electrocardiologist , the overestimation of the method potentialities and the absence of the commonly accepted language of ECG interpretation. The necessity is emphasized of the clear cut differentiation between the electrophysiological and clinical-morphological approaches to the formation of the language of ECG interpretation. The clinical-morphological approach in clinical practice is acceptable only provided that the electrocardiologist is acquainted with the clinical picture of the disease. The use of this approach disregarding the clinical findings constitutes one of the causes of diagnostic errors and iatrogenia .