Older patients have higher in-hospital and longer term mortality after myocardial infarction. To determine if larger infarct size correlates with this observation, myocardium at risk was measured on arrival to the hospital in 347 patients with acute myocardial infarction, and final infarct size was measured at hospital discharge in a subset of 274 of these patients. Myocardium at risk and final infarct size were quantified by tomographic technetium-99m sestamibi imaging. Statistical analyses examined the associations between age, myocardium at risk, final infarct size, and both in-hospital and postdischarge mortality. Median value for age was 64 years, and myocardium at risk was 24% and final infarct size was 12% of the left ventricle. There was no correlation between age and myocardium at risk (r = 0.04, p = NS) or final infarct size (r = 0.06, p = NS). In-hospital mortality was 4% overall and was 2% for patients <65 years old versus 6% for those > or =65 years old (chi-square 11.3, p<0.001). In-hospital mortality was not associated with myocardium at risk (chi square <1, p = NS). For the subset of 274 patients in whom final infarct size was measured, the subsequent 2-year mortality rate was 3% and was independently associated with both age (chi-square 15.6, p<0.001) and final infarct size (chi-square 9.7, p = 0.002). Survival was excellent for patients who were either <65 years old (2-year mortality 1%) or had an infarct size <12% (2-year mortality 0%). For patients > or =65 years old with infarct size > or =12%, 2-year mortality was 13%. These results demonstrate that older patients do not have larger infarcts. Advanced age is associated with higher in-hospital and postdischarge mortality, independent of infarct size.