Background and Objectives: Currently, the patient's baseline situation is a more important prognostic factor than age. The purpose of this study is to estimate the prognostic value of the ISAR score (Identification of Senior at Risk) in patients ≥75 years admitted to intensive care (ICU)., Patients and Methods: Prospective multicenter study including patients ≥75 years admitted to the ICU > 24hours. On admission, 28 days and 6 months after discharge from the ICU, mortality and baseline were evaluated using the ISAR score, the Lawton and Brody scale (LB) and the Barthel index (BI), the Frail fragility scale. scale (FS), the Charlson comorbidity index (ICC), Dementia rating score (DRC)., Results: 38 of 94 patients (40%) were high risk (ISAR ≥ 3) and were characterized by BI 90 (65-100), LB 4 (3-5), and CDR 1 (0-2), ICC 7.5 (6-10). 58% had FS ≥ 3. In the long term, they were in a situation of dependency [BI 50 (2.5-77.5), LB 3 (0-4), CDR 1 (0-1.5)]. The ICU mortality at 28 days and 6 months was 18.4%, 25.7% and 35.3%, respectively, being statistically significant. The area under the ISAR score ROC curve was 0.749 to 0.797, in all the mortality periods studied, although the difference with other predictive variables was not significant, but the p value was the lowest., Conclusions: The ISAR score predicts mortality in critically elderly patients with a discriminative capacity comparable to other predictive variables., (Copyright © 2020 SEGG. Publicado por Elsevier España, S.L.U. All rights reserved.)