This books describes the reengineering of Siemens MagicSAS HIS/RIS interface. MagicSAS is a proprietary software system from Siemens and is used for data administration of a radiology examination. The interface objectives is the comparison and transfer of examination data between the hospital information system (HIS) and radiology information system (RIS). The book introduces the process of reengineering the HIS/RIS interface. First the functionality and qualifying the objectives of the interface are characterized. Based on this, a strategy of reengineering the interface is defined, which alleviates the comprehension of the workflow. Detailed information is given on the implementation of the reengineering strategy, which consists of the establishment of the interface documentation, the used reengineering methods and patterns and the introduction of a logging system. All the performed improvements are validated by a installed test environment. Different regression tests prove the correct functionality of the reengineered interface. At the end of the book an overview of achieved and open goals as well as an outlook regarding future improvements of the HIS/RIS interface are given.