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Electrocardiograme ond bipolar, augmented unipolar limb leads and base-apex lead were recorded from 20 adult and both sexes of mules. Evaluation of 140 traces of ECGs shown that 7 of mules have arrhytmias. Arrhythmias included, sinoatrial block (1), 2nd degree atroventricular block (1) and siuns aarrhytrnia (5). Slight exercise aboished all of these arrhythmias. Nome of the mules showed any signs of hteart disease, that is: edema, jugular distension and pulation, and cardiac murmurs. Therefore, these can be conisidered as physiological or vagal mediated arrhytmias. these arrhythmias have no clinical importance and their diagnosis is very important.