This chapter focuses on the bundle branch reentry (BBR). This chapter also discusses the mechanisms of the BBR. Isolated BBR beats can be found in up to 50% of patients with normal intraventricular conduction undergoing electrophysiology studies; it is a finding without any prognostic significance. The induction of isolated BBR beats or sustained BBR tachycardia share a common mechanism. This chapter also describes the clinical characteristics of patients with BBR- ventricular tachycardia (VT). Left ventricle dysfunction with low ejection fraction and congestive heart failure are typical findings of BBR-VT. Radiofrequency catheter ablation of the RBB is the treatment of choice for BBR-VT. This procedure will eliminate both types of BBR (left bundle branch block and right bundle branch block) by creating complete conduction block in the RBB. Electrophysiologic characteristics of patients with BBR-VT and differential diagnosis of BBR-VT are also discussed in this chapter.