Background: The aim of this study was to evaluate normal subjects with isolated left bundle branch block (LBBB) using tissue Doppler imaging (TDI) for the presence of intraventricular asynchrony. Methods and Results: For this purpose, 23 subjects with isolated LBBB were compared with age-matched asymptomatic healthy subjects without LBBB with respect to global ejection fraction (EF) and isovolumic contraction time (ICTm) in separate left ventricular segments. TDI evaluation revealed prolongation of the ICTm in all of the segments in the LBBB group. Moreover, the ICTm differed significantly in each segment in the LBBB group. The ICTm in the lateral segments were shown to be longer compared to the anteroseptal segments. Conclusion: Our results indicate the presence of intraventricular asynchrony in isolated LBBB. This fact may play a role in the decreased global EF and increased cardiac mortality in patients with isolated LBBB.