Aim:To study all the elderly patients (≥75 years) who were admitted in an Intensive Care Unit (ICU) of a Spanish hospital and identify factors associated with mortality.Patients and Methods:A retrospective, observational data collected prospectively in patients ≥75 years recruited from the ICU in the period of January 2004 to December 2010.Results:During the study period, 1661 patients were admitted to our unit, of whom 553 (33.3%) were older than 75 years. The mean age was 79.9 years, 317 (57.3%) were male, and the overall in-hospital mortality was 94 patients (17% confidence interval 14–20.3%). When comparing patients who survived to those who died, we found significant differences in mean age (P = 0.001), Acute Physiologic Assessment and Chronic Health Evaluation II and Simplified Acute Physiology Scoring II (SAPS II) on admission (P < 0.0001, postoperative patients (P = 0.001), and need for mechanical ventilation (P < 0.0001). Comparing age groups, we found statistically significant differences in SAPS II (P = 0.007), diagnosis of non-ST-segment elevation myocardial infarction (P = 0.014), complicated postoperative period (P = 0.001), and pacemaker (P = 0.034). Mortality between the groups was statistically significant (P = 0.004). The survival between the group of 65 and 74 years and patients >75 years was not significant (P = 0.1390).Conclusions:The percentage of elderly patients in our unit is high, with low mortality rates. The age itself is not the sole determinant for admission to the ICU and other factors should be taken into account.