In a retrospective study, the serial electrocardiograms of all patients with surgically induced right bundle-branch block (RBBB) were reviewed. None of these patients had had RBBB prior to operation. Seven patients who had RBBB from 6 to 16 days after operation showed resolution in ECGs done 3 to 8 months later. Two patients are reported, with documentation by vectorcardiogram, in whom RBBB resolved by 3 and 12 years after operation. The origin of transient forms of RBBB may be different from the long-standing form. If RBBB of long duration is due to operative injury to the proximal right bundle, Purkinje fiber network, or distal branch or branches of the right bundle, or to combinations of these tracts, one may speculate about the possibility of regeneration of the right ventricular conduction system. Since no data are available concerning the long-term prognosis of RBBB and since a progressive conduction disturbance can occur, the resolution of RBBB after many years might carry a better prognosis than its persistence.