The overall objective of this thesis is the development of a management methodology for uncertainty information - uncertainty management for short - in integrated product development. 1 On the one hand the research is guided by the general need to manage uncertainty information and soft knowledge; on the other hand uncertainty management has been found to increase flexibility and significantly reduce development lead times. As integrated product development is an information processing system, at the core of the work is the application of elements of a generalized information theory to supporting information systems. In particular, the uncertainty theories of fuzzy sets and possibility theory and their integration with object database technology promise a new type of information system that can provide more complete and accurate models of reality.