Interoperability is the challenge involved in getting software components to work together. This working session discusses in depth the state of the art in reengineering tool interoperability. A distinction is made between data interoperability and service interoperability. The limitations and promise of each of these aspects of interoperability will be introduced. Examples of existing solutions and an examination of the ways they can be improved to further enhance the reengineering process will be discussed. An evaluation of open problems will show future research perspectives in reengineering tool interoperability.