In a 5-week span during the 1918 influenza A pandemic, more than 2000 patients were admitted to Cook County Hospital in Chicago, with a diagnosis of either influenza or pneumonia; 642 patients, approximately 31% of those admitted, died, with deaths occurring predominantly in patients of age 25 to 30 years. This review summarizes basic information on the biology, epidemiology, control, treatment and prevention of influenza overall, and then addresses the potential impact of pandemic influenza in an intensive care unit setting. Issues that require consideration include workforce staffing and safety, resource management, alternate sites of care surge of patients, altered standards of care, and crisis communication.