Sudden death and syncope are well-recognized clinical manifestations of valvular aortic stenosis (AS). Furthermore, patients with left ventricular hypertrophy due to hypertension have a greater prevalence of late potentials (LP) compared with normal subjects. Chronic pressure overload in AS is frequently characterized by development of left ventricular hypertrophy. The aims of this study were (1) to determine the prevalence of LP in patients with moderate to severe AS, and (2) to investigate the relationship between LP and left ventricular hypertrophy. Signal-averaged electrocardiograms (SAECG) were recorded using a 40 Hz high pass filter in 32 patients (19 M and 13 F), aged 69 +/- 11 years with AS, and in 25 age- and sex-matched controls. QRS duration (QRSD) < 114 ms, low amplitude signal of last 40 ms (LAS40) < 38 ms and root mean square voltage of last 40 ms (RMS40) > 20 microV were considered normal. LP were considered to be present if at least two of the above criteria were abnormal. Each patient underwent a complete echo-Doppler examination and the following parameters were measured; aortic valve area, fractional shortening, left ventricular end-diastolic diameter and mass index. Coronary arteriography was performed in 17 (53%) patients. LP were present in 8 out of 32 (25%) AS patients and in 1 out of 25 controls (4%); this difference was statistically significant (P < 0.006). No difference with regard to age, sex, presence of congestive heart failure, angina, syncope, complex ventricular arrhythmias and coronary artery disease was found in AS patients with and without LP. No correlation was found between indices of left ventricular structure and function and each SAECG parameter. In conclusion, the prevalence of LP in patients with AS is higher than in controls and the presence of LP in AS might be related to factors other than coronary artery disease and left ventricular mass and/or function.