Of 5,132 consecutive patients who had coronary arteriography for chest pain, 103 (2%) had right bundle branch block (RBBB), 66 (64%) of whom had no electrocardiographic evidence of concomitant myocardial infarction (MI); 23 patients had evidence of MI of the inferior wall, 8 of the anterior wall and 6 of the lateral wall. The incidence, location or severity of coronary artery disease (CAD) in patients with RBBB alone were not significantly different from those in 110 similarly symptomatic patients with normal ECGs. However, significantly more left ventricular contraction abnormalities, especially in the anteroapical area, were found in patients with RBBB (p less than 0.01). Similarly, patients with RBBB and inferior MI, compared with 60 similarly symptomatic patients with inferior MI without RBBB, showed no significant differences in location, incidence or severity of CAD. However, more left ventricular contraction abnormalities in the apical area were found in patients with RBBB (p less than 0.025). Thus, the presence of RBBB does not suggest more severe or extensive CAD; however, RBBB does predict more left ventricular contraction abnormalities.