Using 24-hour ambulatory electrocardiographic (ECG) monitoring, the incidence of cardiac dysrhythmias was investigated in 50 apparently healthy elderly subjects aged over 60 years. There was a high incidence of both ventricular and supraventricular ectopic beats, supraventricular tachycardia and sinus arrest. First- and second-degree block were also noted. The incidence of dysrhythmias bore no obvious relationship to age over 60, sex, blood pressure, cigarette smoking, caffeine and theophylline ingestion or resting 12-lead ECG abnormalities.