BACKGROUND: Previous studies have suggested suboptimal use of cardiac medications for secondary prevention after myocardial infarction (MI) and atrial fibrillation (AF), especially among older people. OBJECTIVE: To determine whether patients older than 75 years are less likely than those aged 65 to 74 to be prescribed medications with evidence-based indications, including angiotensin-converting enzyme (ACE) inhibitors for left ventricular dysfunction (LVD) and/or diabetes mellitus (DM), aspirin and/or β-blockers for those with a history of MI, and warfarin for chronic AF. DESIGN: A retrospective cohort study. SETTING: Twenty-nine hospitals, predominantly tertiary-care institutions. PARTICIPANTS: A total of 407 patients randomized to ventricular or dual-chamber pacing from February 26, 1993, to September 30, 1994, in the Pacemaker Selection in the Elderly (PASE) trial. MEASUREMENTS: A review of the patient's medical history and a physical exam at study enrollment, three follow-up timepoints, and a study closeout. RESULTS: Patients older than 75 years with LVD and/or DM were less likely to be prescribed ACE inhibitors (OR = .56 (0.31-1.00)); patients older than 75 with a history of MI were less likely to be taking aspirin (OR = .43 (0.19- .95)), and patients older than 75 with AF were less likely to be prescribed warfarin (OR = .18 (0.05-.61)). Patients older than 75 years of age with any or all of the conditions studied were less likely to be prescribed indicated medications than those ages 65 to 74 (OR = .35 (0.18-.70)), after controlling for between-group differences in comorbidity, gender, and number of noncardiac medications. CONCLUSION: Older age is a significant independent negative correlate of evidence-based cardiac medication use in this cohort. Causes for this finding need to be explored.