CCI patients are patients who have suffered acute illness or injury and require life support or care in an ICU setting for periods of weeks or months. These patients account for between 5% and 10% of ICU admissions, and they appear to be increasing in number. Over half of the patients are over age 65. Patients with underlying premorbid conditions who suffer complications of acute illness are at highest risk for becoming CCI. These patients have poor short-term and long-term survival, although survival may be improving for some types of CCI patients as the medical system adapts to their specific needs. Long-term survival is associated with age and premorbid condition or functional status. Survivors have significant functional limitations, but their reported quality of life is generally good. CCI patients consume a disproportionate share of ICU and hospital resources, and significant additional resources are required for continued recovery or care after discharge. Specialized units have been evolving to manage these patients at lower costs than in acute ICUs, and with similar outcomes. Further refinement of the definition of CCI is an important objective, and should pave the way to better design of outcomes studies. Efforts should continue to learn how to identify patients at high risk for CCI and poor outcome so that expensive resources can be managed effectively, and patient-provider decision making can be better informed.