The authors present a retrospective study of 46 consecutive patients aged from 70 to 79 years (mean 73.3 +/- 2.5 years) with suspected coronary artery disease who, being unfit for exercise tests, were explored by myocardial scintigraphy with thallium 201 after coronary dilatation with intravenous dipyridamole. The examination was well tolerated by 30 patients. Such classical side-effects as chest pain, malaise, dizziness, headache, flushing, vomiting and transient arrhythmia or repolarization disorders were recorded, but they were not more frequent than in younger subjects. However, the occurrence of severe hypotensive malaise relieved by theophylline in two cases and of angina in about one third of patients with myocardial ischaemia means that the procedure must be performed under close supervision. A fall in blood pressure (-11 mmHg on average) and a rise in heart rate (+8 beats/min on average) were usual. Post-scintigraphy follow-up of patients over a mean period of 11.1 +/- 6.2 months showed that a reversible defect of thallium 201 uptake, due to redistribution, is a highly selective indicator of patients who are particularly exposed to a cardiac accident in the short--or mid-term. Only one out of 26 patients without reversible ischaemia (4 p. 100) subsequently presented with a major coronary event (unstable angina). In contrast, in the group of 20 patients with reversible ischaemia three required early myocardial revascularization; furthermore, five serious accidents (29 p. 100) occurred among the 17 patients who were left under medical treatment, including two sudden deaths, two cases of unstable angina and one case of myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)