To determine the frequency of atrioventricular conduction disturbances in aortic valve disease, 26 consecutive patients (age 54 +/- 2 years) with symptomatic aortic valve disease were studied by His bundle electrocardiography at the time of cardiac catheterisation and were compared with a group of patients who underwent cardiac catheterisation and were found to have coronary artery or mitral valve disease but no aortic valve disease. Patients with aortic valve disease had significantly longer PR, AH, and HV intervals than cardiac patients not having this abnormality. Patients with aortic stenosis had prolonged HV, 52 +/- 6 vs +/- 42 +/- 2 ms (P = 0.06), whereas patients with chronic aortic regurgitation had prolonged PR, 245 +/- 27 vs 163 +/- 5 ms (P less than 0.001), and prolonged AH, 178 +/- 30 vs 102 +/- ms (P less than 0.001). Patients with combined lesions had significant prolongation of PR, AH, and HV intervals. Three patients with acute aortic regurgitation caused by endocarditis had normal atrioventricular conduction. Though the presence of valvular calcification did not significantly alter the pattern of atrioventricular conduction in these patients, those with calcified aortic valves had longer HV (P less than 0.005) than the control group. In addition, ventricular dysfunction or coronary artery disease did not affect the pattern of atrioventricular conduction in these patients. Thus, atrioventricular conduction disturbances are common in symptomatic aortic valve disease. With aortic stenosis the site of delay occurs more frequently below the His deflection, whereas in aortic regurgitation it is more frequent above the His deflection.