His bundle pacing (HBP) is a recently developed pacing technique that can achieve an ideal physiological pattern of ventricular activation via stimulation of the native His-Purkinje system. Despite the widespread introduction of HBP in clinical practice, its appropriate indications are yet to be determined clearly. Moreover, the efficacy and safety of HBP and long-term prognosis of patients undergoing such are unknown.We conducted a multicenter observational prospective study in patients undergoing HBP in Japan. Patients with atrioventricular block or conduction delay and estimated ventricular pacing of ≥ 40% scheduled for HBP implantation are included. All patients are followed up until 3 years after the implantation. The primary endpoints are all-cause death, heart failure-related hospitalization, and upgrade to cardiac resynchronization therapy. The secondary endpoint is changes in cardiac function based on echocardiographic findings and laboratory data after the implantation.The results are currently under investigation.This multicenter observational study evaluates the long-term prognosis and changes in cardiac function of patients undergoing HBP implantation in a clinical setting. Considering the large number of patients included, the cumulative results would be helpful in establishing evidence on HBP application in this area and consequently allow accurate management and treatment of patients undergoing HBP.