The usefulness of exercise testing (ET) in old age is so far undefined particularly for detection of arrhythmias. We compared the diagnostic value of ET with 24-h long-term ECG recording (LT-ECG) in patients older than 70 years that were evaluated because of symptoms possibly related to arrhythmias. In 37 patients (age 72.8 +/- 2.7 years) the incidence of ventricular arrhythmias (LOWN greater than or equal to 1) was greater during ET (67%) than during 24-h LT-ECG recording (48%, P less than 0.01). Complex ventricular arrhythmias were detected in 6/37 patients (16%) by ET, in 9/37 patients (24%) by LT-ECG, in one patient (3%) by both tests and in 14/37 patients (37%) by one of the two tests, while 23/37 patients (63%) had no significant complex arrhythmias recorded by either test. During ET 12 patients (32%) showed signs of myocardial ischaemia with ST-depression greater than or equal to 0.2 mV and/or increasing angina pectoris. In 42% of these patients complex ventricular arrhythmias LOWN greater than or equal to 3 occurred during ET. Thus both ET and LT-ECG are useful methods to uncover arrhythmias in symptomatic patients older than 70 years and have to be considered as complementary tools.