Wide QRS complex tachycardias present significant diagnostic and therapeutic challenges to emergency physicians, cardiologists, anesthaesiologists, and intensive care doctors. Wide QRS complex tachycardias have to be initially considered as ventricular tachycardia before any other investigation even if this origin is supraventricular. The first step is to determine the tolerance of the tachycardia. If the tachycardia is associated with syncope, cardiac arrest, severe hypotension or angina, DC cardioversion is mandatory. If the tachycardia is well tolerated, the bedside diagnosis should take into account the clinical context, clinical history and analysis of the surface 12 leads ECG. This article presents the diagnostic and therapeutic approaches to wide ORS complex tachycardias.