Aim of the workThe aim of this study was to compare manifest and concealed accessory pathway regarding:Clinical characteristics such as: gender, prevalence of heartdisease, age of onset of symptomatic tachycardia, incidence of pre-excited AF, Frequency of hospitalization, and episodes of pre-syncope.Electrophysiological characteristics such as anatomical site of accessory pathway, the retrograde electrophysiologicalproperties, inducability of other types of reentrantarrhythmia.Radiofrequency ablation success rate, number of ablationtrials, and complications.Long term follow up regarding: recurrence rate, and need for redo.