One-hundred and ten patients referred for echocardiography to exclude a cardiac source of cerebral emboli were prospectively studied. Four patients with known cardiac abnormalities, for which they were receiving inadequate anticoagulation, were excluded from the study, and 18 patients were subsequently found to have a non-embolic cause for their cerebral pathology. Twenty-eight patients with a normal clinical examination, chest X-ray and electrocardiogram, and 27 patients with hypertension alone had echocardiograms which did not reveal a cardiac source of embolus. Of the remaining group of 33 patients, six were found to have a probable cardiac source of embolus and nine had abnormalities which may be associated with cerebral emboli. Echocardiography may not be indicated in patients with a normal clinical examination, chest X-ray and electrocardiogram, and in patients with hypertension alone. However, if these patients are excluded echocardiography gives a high yield of positive findings which may be of practical importance in the management of the patient.