Twenty-four hour ambulatory electrocardiography was performed on 28 patients with aortic stenosis without significant coronary artery disease or aortic regurgitation. Compared to a control group of subjects with normal hearts proven by noninvasive and invasive testing, patients with aortic stenosis had higher (p = 0.0001) frequency of premature ventricular contractions (PVC) (3144 +/- 1425 versus 17 +/- 46) per 24 hours and higher (p = 0.001) prevalence of PVC presence (27 of 28 patients versus 39 of 101 normal), and complexity (19 of 28 patients versus 4 of 101 normal). Weak correlations of complexity with left ventricular end-diastolic pressure (r = 0.30) and ejection fraction (r = -0.25) were noted. No correlation of ventricular ectopic activity with peak systolic gradient, aortic valve area, or peak left ventricular systolic pressure was noted. Repeat 24-hour ambulatory electrocardiography performed on 13 patients three months after successful aortic valve replacement did not show significant effect of aortic valve replacement on PVC frequency or complexity.