Tightening government regulations and higher customer expectations are driving the increasing usage of electronics in motor vehicles. The higher electronic content in vehicles manifests itself as more on-board microprocessors and sophisticated actuators and sensors. In order to successfully leverage the higher degrees of freedom in control loops afforded by these new actuators and sensors, the complexity of the control algorithms is increasing tremendously. Added to this, the collapsing product development times demand robust high quality techniques for the development of the embedded control systems.This paper describes the model-based embedded control system development process with emphasis on use of rapid-prototype controllers and Hardware-in-the-loop (HIL) testing. Use of model-based embedded control system development by itself cannot identify and address all the problems and potential failure modes of the control algorithm as some of these modes could be due to downstream processes. Rapid controller prototyping enables the designer to migrate and test the new/improved functionality of a control algorithm from a concept to a working prototype in a very short duration. In a typical development process, once the design is verified, it is converted to object code and downloaded to the production controller module. Now it is necessary to verify the functionality of the embedded software operating on the production controller module. HIL testing plays a critical role at this stage by providing the ability to test the production controller module (and software) in real-time conditions and under conditions that would be too expensive or even impossible to replicate on real physical hardware. The concepts of controller rapid-prototyping and HIL testing would be illustrated in the final paper with a case study involving the development of a supervisory controller for a series hybrid electric vehicle.