The feedback control of nonlinear differential and algebraic equation systems (DAEs) is a relatively new subject. It has generated growing interest inspired by its engineering applications and by advances in the feedback control of nonlinear ordinary differential equations (ODEs). This book introduces readers to the inherent characteristics of nonlinear DAE systems and the methods used to address their control. It then discusses the significance of DAE systems to the modeling and control of chemical processes. Within a unified framework, the authors present recent results on the stabilization, output tracking, and disturbance elimination for a large class of nonlinear DAE systems.