Wide complex tachycardia (WCT) comprise a broad spectrum of cardiac rhythm abnormalities including supraventricular tachycardia (SVT) with Bundle branch block aberration (BBB) antidromic tachycardia (ADT) and ventricular tachycardia (VT). Electrophysiologic studies remain the definitive way for diagnosis yet still some cases may pose a real challenge for accurate diagnosis and hence successful RF ablation. We studied 51 pts (32 males, and 19 females, having a mean age of 36.2 yrs (range between 11-58 yrs) who presented to the Critical Care Department, Cairo University by 60 different types of WCT. Following clinical evaluation including 12 lead ECG during SR and during tachycardia, and following tachycardia analysis by applying Brugadas approach all pts were subjected to EPS study including PES using wellens protocol for tachycardia induction. During tachycardia we adopted a 3-stepped algorithim based on the VA relationship (dissociation vs association), HV relation if dissociated and earliest atrial activation if associated. Special maneuvers including incremental A. pacing, sensed AN extrastimulus, preexcitation index and paraHissian pacing were required to discriminate VA associated cases, while BB recording, HB activation sequence and relation of H-HN-V variation were required to differentiate cases with H leading, VA dissociation.Results: Out of the 60 tachycardias we studied and by applying Brugadas' approach, we could segregated 20 cases as VT, with an overall sensitivity of 85.7% and specificity of 82.6%. EIectrophysiologically by using our 3-stepped algorithm, 20 (33.3%) cases were diagnosed as aberrant orthodromic AVRT, 9 (15%) as ADT, 6 (10%) as Mahaim RT, 6 (10%) as aberrant AVNRT, 4 (6.7%) as JT, (1.7%) as AFL (with BBB), while 14 (23.3%) were diagnosed as VT. RF ablation was successful in all 6 cases of AVNRT (100% success rate) all Aps axcept 3 (83% success), 5/6 MRT (83% success) 2/4 JT (50%), and the single case of AFL (100%) while in VT cases, RF was successful in 9/11 idiopathic VT (82% success), 1 out of 2 (50%) ischemic VT, but failed in a single VT in DCM pt.In conclusion: (1) VT should not be the default diagnosis of WCT and all cases presenting with WCT should be subjected to EPS, (2) A systematic approach is the key for accurate diagnosis and our suggested 3-stepped algorithm may act as a basic server to achieve such target. (3) Incremental A pacing can differentiate VT from ADT while ventricular extrastimulus, preexcitation index and paraHissian pacing can confirm or exclude septal pathways in cases with VA association (4) BB recording and sequence of His activation can differentiate BBRT from JT, while the relation of H-HNV variation differentiates it from VT of myocardial origin.