Increasing functional complexity and requirements of quality and security, as well as the continuously shortening of innovation cycles of micro controllers form the situation today in automotive systems. This makes a new method of development for electronic and reactive systems necessary. One possibility to accelerate the development and to improve its quality is the process of ‘Rapid Prototyping’ (RP).This paper shows three forms of RP in conclusion with a new development process (CASE), ranging from an abstract system description to the realisation on the target hardware. This process allows the engineer to generate a prototype micro-controller on the base of his specification. In all developmental phases, the prototype serves for tests and validation in real environments. First, methods of the new development process will be presented. Based on it, three forms of RP, corresponding to the developmental phases, will explain which problems can be solved and which results can be obtained. The RP-process was realized on a VME bus system with a 680X0 CPU-board, several input/output (I/O) -boards and the target-micro-controller under the real-time operating system VxWorks. This computer configuration allows comfortable simultaneous engineering on different development environments, as well as a quick reorganisation of any micro-controller.Finally the benefits of this RP process are presented.