IMPORTANCE: Approximately half of recurrent strokes occur within days and weeks of an ischemic stroke. It is imperative to identify patients at imminent risk of recurrent stroke because recurrent events lead to prolonged hospitalization, worsened functional outcome, and increased mortality. OBJECTIVE: To test the validity of a prognostic score that was exclusively developed to predict early risk of stroke recurrence in a multicenter setting. DESIGN, SETTING, AND PARTICIPANTS: This hospital-based cohort study examined patients with and without magnetic resonance imaging-confirmed recurrent stroke within 90 days after an ischemic stroke. The study was performed at 3 teaching hospitals in the United States, Brazil, and South Korea and comprised adult patients admitted within 72 hours of symptom onset with a magnetic resonance imaging-confirmed diagnosis of acute ischemic stroke. Recruitment to the US cohort was performed from June 1, 2009, through April 30, 2011. Recruitment to the Korean and Brazilian cohorts was performed from January 1, 2007, through December 31, 2011. Data analysis was performed from June 1, 2013, to December 31, 2014. MAINOUTCOMES AND MEASURES: The primary outcome was recurrent ischemic stroke as defined by a clinical incident that was clearly attributable to a new area of brain infarction occurring within the 90 days of index infarction. An investigator who was masked to the patient's recurrence status calculated the Recurrence Risk Estimator (RRE) score for each patient based on information available after initial line of testing in the emergency department. We assessed the predictive performance of the RRE by computing the area under the receiver operating characteristic curve. RESULTS: The study included 1468 consecutive patients with 59 recurrent ischemic stroke events. The median age of the patients was 69 (interquartile range, 58-79) years, and 633 (43.1%) were female. The cumulative 90-day recurrence rate was 4.2% (95% CI, 3.2%-5.2%). The mean RRE score was 2.2 (95% CI, 1.9-2.5) in patients with recurrence and 1.0 (95% CI, 1.0-1.1) in patients without. The risk of recurrence increased with a higher RRE score (log-rank test, P <.001). The area under the receiver operating characteristic curve for discrimination was 0.76 (95% CI, 0.70-0.82). The RRE identified 710 patients (48.4%) in the study population as high risk (>10%) or low risk (<1%). The sensitivity and specificity were 38% and 93% for identifying low-risk subsets and 41% and 90% for identifying high-risk subsets, respectively. CONCLUSIONS AND RELEVANCE: This study confirms the validity of the RRE score in a multicenter cohort of patients with diverse characteristics. Our findings suggest that the RRE could be useful in identifying high- and low-risk patients for targeted stroke prevention.