Electrophysiologic studies of His' bundle were done on 32 consecutive patients with symptomatic aortic valvular disease. Nineteen had pure aortic regurgitation and 13 had aortic stenosis, four with significant regurgitation. Fifteen of the former had atrioventricular (AV) and/or intraventricular (IV) conduction abnormalities. In those with aortic stenosis, eight had conduction abnormalities, all intraventricular but one. Twelve of the 13 with aortic stenosis had radiographically indentifiable valve calcification; all four with a peak systolic gradient greater than 80 mm Hg had IV conduction defects. Of the 32 patients, six had A-H prolongation and in all the predominant lesion was aortic regurgitation (one with moderate stenosis). There was no difference in age, clinical congestive heart failure, coronary artery disease, or prolonged H-V interval. However, PR prolongation (P = .01) and decreased ejection fraction (P = .02) was significantly increased in the former group. Patients with aortic regurgitation had longer A-H and H-V intervals (NS), induced A-V block at lower heart rates (P = .01), and higher A-V node effective (P = .001) and functional (P = .01) refractory periods. In summary, patients with aortic valvular disease have a high incidence of atrioventricular and intraventricular conduction disease.