<jats:p>Thirty‐five patients with bundle branch block (BBB) and unexplained syncope underwent electrophysiologic study (EPS) including programmed ventricular stimulation and ajmaline administration (1 mg/kg, IV) to induce inra‐His block. A prolonged HV interval (>55 ms) was present in 16 of the 35 patients. Ajmaline‐induced HV block occurred in 12 patients (complete HV block in 10, and 2:1 HV block in two). Monomorphic ventricular tachycardia (VTJ was inducible in nine (25.7%) and polymorphic VT in two patients (5.7%). Left ventricular ejection fraction (LVEFJ was less than 40% in five patients (45.5%) with inducible VT. Two patients had an unexpected co‐existence o/inducible HV block and VT. The remaining 14 patients (40%) had no detectable abnormality. The incidence of inducible VT was higher (45% vs 13.3%), and the presence of negative studies was lower (30% vs 53.3%) in patients with structural heart disease (n = 20), when compared to those with no significant heart disease (n = 15) (differences not significant [NS]). During a mean follow‐up period of 16.5 ± 9.2 months, all the patients with inducible HV block have been asymptomatic after having received permanent pacemakers. Patients with inducible monomorphic VT (except one with poor left ventricular function who died suddenly) have also been asymptomatic on antiarrhythmic drugs. Of the remaining patients, seven with normal EPS, two with prolonged HV intervals but no inducible HV block (despite being given permanent pacemakers) and one patient with polymorphic VT on antiarrhythmic drugs continue to have recurrent syncope. Approximately 60% of patients with BBB and unexplained syncope have clinically significant electrophysiologic abnormalities. VT accounts for symptoms in a significant number of patients. Ajmaline stress is a useful adjunct to unmask infra‐His block, and some patients have more than one abnormality. Long‐term management guided by detailed EPS is generally successful in preventing recurrent syncope in patients with inducible arrhythmias such as HV block and monomorphic VT.</jats:p>