The authors compared the average electrocardiographic (ECG) intervals in a population of patients 80 years and older with published "normal" values. The medical records of patients who presented to the Mayo Clinic for health maintenance examinations and who had a routine ECG performed (N=702) were selected. Age; sex; rhythm; PR, QRS, and QTc intervals; incidence of cardiac disease; and presence of interval-prolonging medication were recorded. Reference ranges were estimated from the data and compared with standard cutoffs for prolonged intervals. Interval values were significantly higher in men. Reference ranges were established separately for both sexes based on the subset of 578 patients without a history of cardiac disease and not taking interval-prolonging medication. In all instances, the ranges were higher than the recommended cutoffs. The upper limits for prolonged PR, QRS, and QTc intervals were found to be significantly higher in a population of patients older than 80 years.