One hundred and twenty stable patients with pure and severe aortic valve disease and without coronary lesions (aortic stenosis, 43 patients; aortic regurgitation, 45 patients; combined aortic stenosis and regurgitation, 32 patients) who had been submitted to haemodynamic studies were prospectively studied with standard electrocardiograms, M-mode echocardiograms, and 24-hour ambulatory electrocardiography (Holter recording). The frequency and complexity of ventricular arrhythmias were related to clinical parameters such as functional class, type of lesion and presence of syncope, and to parameters of left ventricular hypertrophy and function. Ventricular arrhythmias were present in 92% of patients. A high number of ventricular premature beats was directly correlated with parameters of complexity of the arrhythmia. A significant relation was found between electrocardiographic left ventricular hypertrophy and Ryan class (P less than 0.05), and an inverse relation between maximal number of ventricular premature beats in any hour and left ventricular ejection fraction (P less than 0.05). The group of patients with aortic regurgitation showed a higher total number of ventricular premature beats per 24 hours (P less than 0.001), a higher maximal number of these in any hour (P less than 0.01), a higher number of patients with pairs (P less than 0.001), and a higher number of patients in Ryan classes 3, 4A, 4B (P less than 0.01). This study shows a high incidence of ventricular arrhythmias in aortic valve disease, and especially in aortic regurgitation, with a significant relation between left ventricular hypertrophy and function, and number and complexity of arrhythmias.