In the process of interpreting an electrocardiogram (ECG) the mean electrical axis of the heart needs to be determined. In veterinary electrocardiography the mean electrical axis (MEA) is figured in the frontal plane and can be calculated by using several different ways. In this study, values of the MEA, calculated by two methods (the isoelectric lead method and the vector method), were compared. The aim of this study is to establish whether different methods give different values for MEA. German shepherd dogs of different age, presenting in sinus rhythm, were used in the study. Electrocardiograms (ECGs) were recorded while the dogs were in standard position (right lateral recumbency). The determination of mean electrical axis were performed by examining the QRS complexes in each of the peripheral leads (I, II, III, avR, aVL, aVF). Mean values of the MEA were calculated by two methods were ¯x1 = 76,50º ± 19,83 i ¯x2 = 80,17º ± 11,44. Values of the MEA determined by two methods were not statistically different (p = 0,384). These results show that value of the MEA in healthy dogs is not under significant influence of the method chosen for calculation.