OBJECTIVES: Angiotensin Converting Enzyme Inhibitors (ACEI) and Angiotensin Receptor Blockers (ARB) are popularly used drugs for treatment of heart failure. A 2007 AHRQ-sponsored meta-analysis of clinical trials comparing these two drug classes, and a 2012 follow up, both concluded that there is insufficient evidence that one drug class displays better efficacy. This study aims to evaluate the comparative effectiveness of ACEI versus ARB in elderly (>65 years) patients with heart failure. METHODS: This study used Medicare 5% national sample for the years 2006 to 2008. A retrospective cohort design was employed to study new users of ACEIs or ARBs, matched on propensity scores. Beneficiaries who have heart failure, followed by new therapy with ACEIs/ARBs were included. A 6-month washout period was used to ensure patients are receiving new prescriptions of ACEIs or ARBs. All patients were followed for at least one year from the date of initiation of therapy. All-cause mortality, heart failure readmission, Major Adverse Cardiovascular Event (MACE) were measured. Analysis was conducted using SAS 9.3 (Cary, NC). Survival analysis, with censoring, was conducted to determine the incremental effectiveness of one drug class over the other. RESULTS: A total of 2053 matched pairs of ACEI and ARB users were identified. The sample comprised of 70% females, and 92% Caucasians, with a mean age of 80 years. The hazard ratio for time to mortality, heart failure and the composite outcome were 1.013 (95%CI = 0.953 – 1.077; p = 0.68), 1.038 (95%CI = 0.976 – 1.103; p = 0.24), and 1.024 (95%CI = 0.963 – 1.088; p = 0.45), respectively.  CONCLUSIONS: No significant improvement was found in patients using ARBs over those using ACE Inhibitors. Besides the previously established possibility of side effects from use of ACEI, it appears that they do not offer any worse outcomes than ARB.