The evolution of a design pattern typically involves the addition or removal of a group of modeling elements, such as classes, attributes, operations, and relationships. However, the possible evolutions of each design pattern are often not explicitly documented. Missing part of the evolution process may result in inconsistent evolution. In this paper, we define the evolution processes of design patterns in terms of twolevel transformations, thus making the possible evolutions of each design pattern explicit. In addition, we automate the evolution processes as XSLT transformations that can transform the UML model of a design pattern application into the evolved UML model of the pattern. Both the original and evolved UML models are represented in the XML Metadata Interchange (XMI) format to facilitate the transformations. Furthermore, we check the consistency of the evolution results using the Java Theorem Prover.