As the general population ages, an increasing number of patients over 80 years are being admitted to the intensive care unit (ICU). Selection of older patients for ICU admission results in lower rates of co-morbidities and underlying fatal diseases. After adjustment for disease severity, ICU and post-ICU mortality rates are higher in elderly patients than in younger populations. Age itself explains only a small part of the increased hospital mortality, suggesting that specific information such as functional, cognitive, and nutritional status, as well as co-morbidities, should be collected to predict mortality in elderly ICU patients. The long-term prognosis depends chiefly on functional status, whereas initial disease severity no longer influences mortality. According to our review, it is impossible to define evidence-based recommendations for ICU admission of the elderly. This justifies further studies that encompass several aspects, such as the initial triage process and the long-term prognosis (mortality, autonomy and quality of life).