The purpose of this study was to assess whether the clinical history is of any value in the differentiation in the emergency department of ventricular tachycardia (VT) from supraventricular tachycardia (SVT) with aberration. The records of 84 patients who presented with a wide-complex tachycardia and who were able to provide a history were reviewed. The wide-complex tachycardia was proven by a later electrophysiologic study to be VT in 62 patients and SVT with aberration in 22 patients. History of prior myocardial infarction, history of congestive heart failure, and history of recent angina pectoris all had positive predictive values for VT of greater than 95%, but had sensitivities of 66%, 24%, and 24%, respectively. Age greater than 35 years had a sensitivity of 92% and a positive predictive value of 85% for VT. None of the clinical characteristics was strongly predictive for SVT; the best was age less than or equal to 35 years, which had a positive predictive value of 70%. We conclude that clinical variables may be helpful in the emergency department diagnosis of wide-complex tachycardias. If a patient with a wide-complex tachycardia has a history of myocardial infarction, congestive heart failure, or recent angina pectoris, the tachycardia has a high likelihood of being ventricular in origin. However, there are no clinical variables that are highly predictive of SVT with aberration.