The use of new automatic control systems in automotive applications, added to a vast number of more simple devices, has led to some problems concerning the complexity in the electrical wiring of vehicles. Ln order to solve these problems, a widespread need has been felt for an alternative system of interconnection. This paper is a case study of the application of the IEC/ISA FieldBus, which is a particular digital serial communication system, to the control systems present in a car. The authors deal with the problem of the management of control traffic, exploiting IEC/ISA FieldBus features, and assessing its behaviour in different traffic conditions. Despite the particular application considered, the results obtained have a general validity and show the ability of the FieldBus to meet the communication requirements of time-critical systems.