We present a new approach to the reorganization of object-oriented systems using design patterns. Instead of looking at design patterns as building blocks, we consider them to be operators, whose application transforms an existing design into an improved target design. For this purpose, an algorithmic process of design pattern application is presented. Furthermore we show that design pattern operators can be implemented in terms of refactorings in a behavior preserving way. Afterwards we demonstrate the applicability of our approach by delineating our experiences with a tool prototype, which we implemented in order to reorganize a large C++ system by using design pattern operators.