A survey was made on a population of 6059 subjects aged more than 60 years with the aim to assess 1. the prevalence of heart arrhythmias and 2. the relationships between arrhythmias and some other ecg alterations. Arrhythmias resulted present in 29.0% of the whole population with a significantly higher prevalence among males (30.7% vs 28.1%, P less than 0.05) and among subjects over 75 years of age (33.2% vs 23.9%, P less than 0.001). Supraventricular extrasystoles (SE, 11.55%), atrial fibrillation (AF, 10.44%) and ventricular extrasystoles (VE, 8.91%) were the most frequent arrhythmias, followed by sinus bradycardia (SB, 2.04%), sinus arrhythmia (SA, 1.35%), atrial flutter (AFL, 1.09%) and junctional rhythms (JR, 0.20%). AF and AFL resulted significantly more frequent among females, whilst SE, VE and SB were more frequent among males. All the above arrhythmias, with the exception of AFL and JR resulted significantly more frequent among subjects over 75. A significantly higher prevalence of ecg signs of left ventricular hypertrophy, ischemia, previous myocardial infarction (MI) and of the so-called "minor" T-wave changes (MTC) was found among the subjects with arrhythmia as compared with those free from rhythm disturbances. Ecg signs of MI and MTC were significantly more frequent among males and MTC were more frequent among females and among subjects over 75. It is concluded that in an old person the presence of an arrhythmia should lead to a careful evaluation of the general and cardiological clinical situation in order to avoid 1. to prescribe an unnecessary and potentially dangerous antiarrhythmic treatment, and 2. to misdiagnose an underlying clinical condition liable to a decisive improvement under adequate treatment.