Army transformation has many dimensions with change in technology, operational methods, and organizations. So far, the focus of organizational transformation has been on the redesign of tactical units such as the interim brigade combat teams. But corps--the Army's operational level organizations--must also be transformed. The author provides a history of the structure and function of Army corps and discusses ways they might be redesigned to play an effective role in the 21st century security environment. He concludes that the different Army corps have such diverse functions that a "one size fits all" approach is inappropriate. After considering a number of options, he provides a blueprint for an array of corps structures that would fulfill missions from peacekeeping to major wars.