In the automotive industry, a steadily growing number of mono-functional electronic control units (ECUs) with increasing complexity on the one hand and restrictive requirements for power consumption and mounting space on the other hand are forcing an architectural change in car electronics. Computer platforms with a client/server architecture could potentially reduce the number of ECUs in a car drastically, with a commensurate reduction of costs and space, better integration possibilities for enhanced functionality and additional services during the lifetime of a car.One of the problems which arises when those architectures come to the car is coping with the complexity of mainly software-based functionality and reliability issues under the aspect of rapidly evolving hardware infrastructure. The reorganization of car electronics also offers the possibility of a redistribution of functionality in the car which has been designed in the past for specific demands. In the case of the introduction of a client/server-architecture, it is proposed that a Reference Architecture based on a consistent top-down design process be specified where from further component specifications (e.g. interfaces) can be derived. Compared to a context-less specification of single APIs, a consistent process-based system specification offers a reduction in errors and necessary long-term redesigns.The proposed process-based specification starts with an analysis of the Automotive Domain where from a common Domain Architecture can be identified. A first step from the descriptive Domain Architecture to a high- level implementation is a Sub-systems Architecture wherein sub-systems are defined under later assembly, operational and functional aspects. The Sub-system Architecture is still free from any implementation and therefore might be the basis for a Reference Architecture wherein additional details can be specified to a certain depth depending on business goals, e.g. compatibility to already existing commercial products. A Reference Architecture offers a consistent high-level standardized framework specification of functionality without any restrictions on individual realization. Also it might offer a reference for purchasing components. One of the consequences might be that economies of scale are achieved.In the paper the proposed development process to achieve a Reference Architecture will be described in detail and first results are presented. The paper should serve as the basis for further discussion in the automotive industry.