People over age 65 are the fastest growing segment of the population and account for 42% to 52% of the intensive care unit admissions in the United States. There are many physiologic changes that occur with aging which can impact on both the presentation and management of older patients with critical illness. Older patients have an increased risk for the development of sepsis, and age itself impacts on outcomes related to sepsis. Delirium is also very prevalent among older intensive care unit patients and is associated with adverse outcomes. While outcome studies suggest that chronologic age itself is not a risk factor for poor outcomes after adjusting for severity of illness, older patients clearly have physiologic changes which need to be considered when providing critical care. This article will review important physiologic changes of aging, as well as sepsis and delirium and outcomes of older ICU patients.