Hypertension is common in older persons (2 in 3 have the condition) and a major reason to see doctors and take medications. The condition poses substantial burden by increasing the risk of ischemic heart disease (IHD), heart failure (HF), and stroke. Commonly used two classes of drugs, angiotensin converting enzyme inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs), are considered to have similar benefit and side effect profiles except for ACEI causing more cough. However, there is very little data to support the similarity of the effect on important clinical outcomes (death or cardiovascular events), especially in older patients and those with serious comorbidities. The known difference, however, is their cost. ARBs are substantially more expensive than ACEIs. We, therefore, propose to compare if one class or specific generic within the class is better than the other preventing more heart attack, HF, or stroke and/or death in older patients with hypertension who already suffer from HF, IHD, or stroke. We will use linked claims databases for the elderly in two US states and employ new user design, validated outcomes, and advanced analytic techniques to control for potential biases. The results will further be validated in subsets which are linked to clinical registries of HF, IHD, or stroke with detailed clinical information. The results will provide actionable information for patients, physicians and policy makers to make decision in uses of these drugs.