When confronted with a tachycardia having a broad QRS complex, it is important to differentiate between a supraventricular tachycardia (SVT) and a ventricular tachycardia (VT). Medication given for the treatment of a SVT may be harmful to a patient with a VT. Electrocardiogram should not only tell how to distinguish VT from other tachycardias with a broad QRS complex, but also to suspect its etiology and its site of origin in the ventricle. Classification of tachycardias with a broad QRS complex, electrophysiology of ventricular tachycardia, criterias to differentiate wide QRS tachycardia, and etiology of ventricular tachycardia are discussed. Value of the electrocardiogram during sinus rhythm, value and limitations of the electrocardiogram in broad QRS tachycardia, management of wide QRS tachycardia are explained.