Background— Prior studies have suggested lower use of guideline-recommended therapy and worse poststroke outcomes in older patients. We sought to examine age-related differences in characteristics, performance measures, temporal trends, and early clinical outcomes for acute ischemic stroke in a large contemporary cohort. Methods and Results— The relationships between age and clinical characteristics, performance measures, and in-hospital outcomes were analyzed in 502 036 ischemic stroke admissions from 1256 hospitals in the Get With the Guidelines–Stroke program from 2003 to 2009. Data were analyzed by age groups (<50, 50 to 59, 60 to 69, 70 to 79, 80 to 89, and ≥90 years) and with age as a continuous variable. Seven predefined performance measures and 2 summary measures were analyzed. Mean age of ischemic stroke patients was 71.0±14.6 years; 52.5% were women. Older patients were more likely to have a history of atrial fibrillation or hypertension and less likely to be black, Hispanic, or current/recent smokers. Although modest age-related differences in each individual performance measure were identified, there were substantial temporal improvements in performance measures from 2003 to 2009 in each age group, and many age-related treatment gaps were narrowed or eliminated over time. Older patients were less likely to be discharged home (adjusted odds ratio, 0.69; 95% confidence interval, 0.68 to 0.69) and more likely to die in hospital (adjusted odds ratio, 1.27; 95% confidence interval, 1.25 to 1.29) for each 10-year age increase. Conclusions— Older patients with ischemic stroke differ in clinical characteristics and experience higher in-hospital mortality than younger patients. Performance measure–based treatment rates improved substantially over time for ischemic stroke patients in all age groups, resulting in smaller age-related treatment gaps.