The poor prognosis of myocardial infarction in old people is based almost completely upon clinical observations. But in the case of patients of advancing years it seems likely that the percentage of undiagnosed infarctions-whether due to atypical symptoms or to the fact that the patient is not admitted to hospital-is considerable. To estimate the level of this percentage a clinical-autoptical analysis of 124 decreased with transmural myocardial scars was carried out (mean age of death: 80 years). This reveals that 80% of all myocardials scars had not hitherto been diagnosed. Only 35% of the electrocardiograms showed definite scars, mostly in the case of patients with known myocardial infarction. 22% of deceased had complained about angina pectoris, again mostly patients with known myocardial infarction. In comparison with other studies of people in the same age group, the results are not surprising. This is only explained in part by old people's poor powers of recollection and their limited ability to communicate. These results indicate that the over all prognosis of acute myocardial infarction in old people, which often does not occur in hospital without being diagnosed should be viewed in a more favourable light than clinical results would suggest.