To determine how often aspirin was prescribed as a discharge medication to eligible patients 65 years of age and older who were hospitalized with an acute myocardial infarction; to identify patient characteristics associated with the decision to use aspirin; and to evaluate the association between prescription of aspirin at discharge and 6-month survival. Observational study. All 352 nongovernment, acute care hospitals in Alabama, Connecticut, Iowa, and Wisconsin. 5490 consecutive Medicare beneficiaries who survived an acute myocardial infarction, were hospitalized between June 1992 and February 1993, and did not have a contraindication to aspirin. Medical charts were reviewed to obtain information on the prescription of aspirin at discharge, contraindications, patient demographic characteristics, and clinical factors. 4149 patients (76%) were prescribed aspirin at hospital discharge. In a multivariable analysis, an increased prescribed use of aspirin at discharge was correlated with several indicators of better overall health status (better left ventricular ejection fraction, absence of diabetes, shorter length of hospital stay, higher albumin level, and discharge to the patient's home). The prescribed use of aspirin at discharge was also associated with several specific patterns of care, including the use of cardiac procedures, β-blocker therapy at discharge, and aspirin during the hospitalization. The prescribed use of aspirin at discharge was associated with a lower mortality rate 6 months after discharge compared with no prescribed aspirin (odds ratio, 0.77; 95% CI, 0.61 to 0.98), even after adjustment for baseline differences in demographic, clinical, and treatment characteristics between the two groups. Aspirin was not prescribed at discharge to 24% of elderly patients who were hospitalized with an acute myocardial infarction and did not have a contraindication to aspirin. Several patient characteristics were associated with a higher risk for not being prescribed aspirin. Increasing the prescription of aspirin for these patients may provide an excellent opportunity to improve their care.