A 53 year old woman developed chest pain with transient anterior subepicardial ischaemic ECG changes and a mild increase in serum myocardial enzyme concentrations. She was admitted to hospital some time later but there were no electrocardiographic signs of infarction. Echocardiography was considered to be normal. Coronary angiography showed no significant stenosis and there were no segmental wall motion abnormalities on left ventriculography. The diagnosis of a non-Q wave infarct was confirmed by myocardial scintigraphy using antimyosin monoclonal antibodies labelled with Indium 111. The site and size of the necrosis were also determined by this non-invasive investigation.