Inst. fur Informationssyst., Eidgenossische Tech. Hochschule, Zurich, SwitzerlandAbstract: During the last several years, reengineering methods and tools have gained increasing interest. The reengineering of data intensive applications often encompasses an appropriate evolution of the data, too. But the data has to be migrated to a new environment, not only when an application system gets reengineered but also when hardware and/or software components are replaced by newer ones. Moreover, because data is one of the most expensive components of an application system, there can be considerable economical advantages if, instead of reentering data into a new system, it is possible to use data from other systems which are already operational. In these cases, the data has to be prepared thoroughly to be useful for such a multi use. All these activities can be paraphrased with the notion: data reengineering. Some data reengineering problems are discussed and a process model for data reengineering projects is introduced.