Cardiac rhythm was studied by means of 24-hour ambulatory ECG in 18 active outpatients, mean age 92.3 +/- 2.3 years. The main characteristics observed were the following: a broad dynamic heart rate range; relatively rare atrial fibrillation (5.5%); incidence of simple atrial and ventricular premature beats, complex atrial premature beats or supraventricular tachycardia in all subjects, while ventricular tachycardia and R-on-T phenomenon were present in only one subject. The 'arrhythmic normality' parameters in the very elderly probably need to be revised, and only severe ventricular arrhythmias appear to be an abnormal phenomenon.