Ventricular ectopy is one of the most common arrhythmias in the dog. It often causes panic among inexperience clinicians who want to treat it as soon as possible when they see it on an ECG. Ventricular arrhythmia can be caused by cardiac or extra cardiac disease and the latter includes systemic, abdominal or CNS disease. Three major points need to be evaluated prior to treatment: ¿Is the arrhythmia complex? ¿Has the patient got clinical signs or haemodynamic effects due to the arrhythmia? ¿Is the underlying disease transient or persistent? This approach highlights one of the traditional axioms of arrhythmia treatment: treat the patient and not the ECG. The key things to look on an ECG for complexity are: ¿Does the ventricular ectopy present as isolated beats, or as couplets, triplets or ventricular rhythm? ¿How fast is the ventricular rhythm or the coupling interval between couplets? ¿Is the arrhythmia multiform? ¿Are there R on T? ¿How frequent is the arrhythmia over 24 hours? In many occasions the arrhythmia may not need treatment. The treatment is aimed towards the underlying cause. The more common antiarrhythmics used in dogs include lidocaine, sotalol, atenolol, mexiletine and amiodarone. During the talk I will describe and discuss all these points in great depth. The attendants are expected to improve markedly their confidence in diagnosing and treating ventricular arrhythmia.