A wealth of useful diagnostic criteria is available to assist the health care worker in arriving at the correct diagnosis in cases of a wide QRS tachycardia (WQRST). Despite the abundance of good criteria for determining the diagnosis in cases of WQRST, they are of no use if they cannot be readily applied in an urgent clinical situation because they cannot be easily recalled or are too complex and cumbersome to use. It may be that refresher courses in the differential diagnosis of WQRST, especially for emergency physicians who are often the "first responders" to patients with WQRST, can improve physicians' diagnostic accuracy in this important disorder.