SUMMARY Acromegaly is associated with an increased cardiac morbidity and mortality, but it is not clear whether this is the result of increased incidence of hypertension and coronary heart disease or of a specific disease of heart muscle. Thirty four acromegalic patients were studied by non-invasive techniques. Seven of these patients had raised plasma concentrations of growth hormone at the time of study; three were newly diagnosed and had not received any treatment. This is the first study to find evidence of subclinical cardiac diastolic dysfunction in acromegaly and it supports the suggestion that there is a specific disease of heart muscle in acromegaly.While systemic hypertension, atherosclerosis, and diabetes mellitus may contribute-to cardiovascular complications in acromegaly, cardiac failure has occurred in patients with acromegaly in the absence of these and other established causes of heart muscle disease.'" Such cases suggest the existence of a specific disease of heart muscle in acromegaly. Post