This paper is concerned with decentralized control problems. There are two typical procedures to design decentralized controllers, 'independent' and 'sequential' design procedures. As the concepts and the techniques in these two approaches are too different from each other, there have been no attempts to unify these approaches. This paper proposes an iterative independent design procedure for decentralized control systems, which is a unified approach to these conventional approaches. (C) 2007 Elsevier Ltd. All rights reserved.