Ambulatory ECG monitoring during everyday activities (AEM) and a multistage submaximal bicycle ergometric test (BET) was performed on a series of 48 patients suffering from precordial symptoms or pain. The results of these tests were compared with the results of coronary arteriography. In 20 subjects with a negative AEM and BET the coronary arteriography was normal in 18, moderately pathological (30-60% narrowing) in 1, and severely pathological (greater than 60% narrowing) in another. In 23 subjects in whom both AEM and BET disclosed ST-T alterations, 20 had severely pathological and 1 moderately pathological coronary arteriograms; normal coronary arteries were found in only 2 subjects. Only 5 of the total of 48 patients of the series showed a discrepancy between the results of AEM and BET. The findings on coronary arteriography confirmed that patients with a normal AEM and BET have a very high probability of having normal coronary arteries, while if both tests are positive the patient will most likely have advanced coronary pathology. When the two tests were concordant, the number of false positive and false negative results were slightly less than if ergometry was performed alone. Although AEM does not provide the quantitative aspect of effort testing, it does have the advantage of avoiding the risk of unusual physical effort for the patient.