Business users have a problem in replacing existing business application systems. Well over 50% of all replacement projects fail. The systems have become much too complex and too much knowledge about them has been lost. It is nearly impossible to reconstruct the requirements. Therefore, this paper presents an incremental, integrative approach supported by bridging tools, which allows migrating without requirements. The basic premise is to first breakup the existing systems into separate, collaborating subsystems and then to either convert them, redevelop them or to wrap them one at a time. The key is the interaction of the subsystems with each other and with the database across platform boundaries. The new subsystems can coexist with the remaining old ones until such time that all of them have been replaced.