Background: Age- related differences in patients with an acute coronary syndrome(ACS) have not been well characterized in prior observational studies that often included only certain age groups or subjects with myocardial infarction(MI). Methods: We stratified 4627 patients admitted with an ACS across 9 provinces between 1999 and 2001 enrolled in the Canadian ACS Registry into 3 age groups(< 65, 65- 74, and ≥ 75 years)to evaluate differences in clinical characteristics, management, and 1- year outcome. Results: Older patients more frequently had previous angina,MI, or heart failure and were less likely to have positive cardiac markers, ST elevation, and Q- wave MI or to receive thrombolytics, β - blockers, and cholesterol- lowering and antiplatelet agents in hospital, at discharge, and at 1 year. In multivariable analyses controlling for patient factors, every decade increase in age was independently associated with reduced use of coronary angiography(odds ratio [OR] 0.79, 95% CI 0.74- 0.84, P< .001) and percutaneous coronary intervention(OR 0.88, 95% CI 0.81- 0.95, P=.001). When adjusted for validated clinical prognosticators and differences in management, every decade of age increment independently predicted an increased risk of death at 1 year(OR 1.87, 95% CI 1.66- 2.12, P< .001). Conclusions: Across the broad spectrum of ACS, elderly patients had more complex comorbidities and worse outcome, yet they were less likely to undergo revascularization or to receive acute and long- term evidence- based medications. Our findings emphasize the ongoing need to better define and promote optimal therapeutic regimens for elderly patients with ACS. Background: Age-related differences in patients with an acute coronary syndrome (ACS) have not been well characterized in only prior to observational studies that often included only certain age groups or subjects with myocardial infarction (MI). Methods: We stratified 4627 patients admitted with an ACS across 9 provinces between 1999 and 2001 enrolled in the Canadian ACS Registry into 3 age groups (<65, 65- 74, and ≥ 75 years) to evaluate differences in clinical characteristics, management, and 1-year outcomes. Results: Older patients more of had previous angina, MI, or heart failure and were less likely to have positive cardiac markers, ST elevation, and Q-wave MI or to receive thrombolytics, β-blockers, and cholesterol- lowering and antiplatelet agents in hospital, at discharge , and at 1 year. In multivariable analyzes controlling for patient factors, every decade increase in age was independently associated with reduced use coronary angiography (odds ratio [OR] 0.79, 95% CI 0. 74- 0.84, P <.001) and percutaneous coronary intervention (OR 0.88, 95% CI 0.81-0.95, P = .001). When adjusted for validated clinical prognosticators and differences in management, every decade of age increased independently predicted an increased risk of death at 1 year (OR 1.87, 95% CI 1.66-2.12, P <.001). Conclusions: Across the broad spectrum of ACS, elderly patients had more complex comorbidities and worse outcome, yet they were less likely to mutational revascularization or to receive acute and long-term evidence-based medications. Our findings emphasize the ongoing need to better define and promote optimal therapeutic regimens for elderly patients with ACS.