Intensive care units (ICUs) are dynamic organizations with one of the most complex environments of all healthcare facilities. Defining or measuring ICU performance is, therefore, challenging. The meaning, scope, and measurement of performance in health care has evolved and expanded over the past two decades. Some of the most widely used approaches to improving performance in health care have proved inadequate, all the more as, since 2000, healthcare organizations are faced with increasing challenges, including changing demographics, increased customer expectations, increased competition, and intensified governmental pressure, that demand unprecedented levels of change. Meeting these challenges will require healthcare organizations to undergo fundamental changes and to seek new ways to improve performance.