The equine practitioner is faced with a wide variety of dysrhythmias, of which some are physiological. Therecording of an exercise electrocardiogram (ECG) can help distinguish between physiological and pathologicaldysrhythmias, underlining the importance of exercise recordings.The evaluation of an ECG recording should be performed in a highly methodical manner in order to avoiderrors. Each P wave should be followed by a QRS complex, and each QRS complex should be preceded by aP wave.The classification of dysrhythmias according to their origin helps to understand the associated changes onthe ECG. In this respect, sinoatrial nodal (SA nodal), atrial myocardial, atrioventricular nodal (AV nodal) andventricular myocardial dysrhythmias can be distinguished.Artefacts on the ECG can lead to misinterpretations. Recording an ECG of good quality is a prerequisiteto prevent misinterpretations, but artefacts are almost impossible to avoid when recording during exercise.Changes in P or T waves during exercise also often lead to misinterpretations, however they have no clinicalsignificance.