The use of model-based methods for the support of the planning, designing, and operating of chemical processes and plants has recently gained increasing importance in the daily work of the process engineer. However, it is becoming more obvious that already the design of mathematical models by the use of standard flowsheet simulation tools requires an experienced designer. Therefore, the developed models not only represent a value considering the resources required for their development, but especially they contain a large amount of knowledge of an enterprise about its products and production processes. It is hence reasonable to lower the costs of model development by reuse of models and experiences. This report gives an overview about the systematic long-term management and use of mathematical models. Some motivating scenarios help to derive requirements for a model management system and to evaluate existing methods and tools. From these results, the concept of a model management system is derived. After presenting a prototypical implementation, this article concludes with an outlook.