Abstract: This paper presents a reliable gateway for communication between the LIN, CAN, FlexRay protocols. A gateway is indispensable device for constructing in-vehicle networks. Networks with different protocols have to include an additional gateway in order to exchange information among different networks. The main function of the gateway is translation. However, there is some latency when a message is transferred from one node (source) to another (destination); further, there is a high probability of error due to different protocol specifications such as baudrates, message frame formats, and so on. Therefore the implementation of a reliable gateway is a challenging task. In this paper, we propose a reliable gateway based on OSEK OS and OSEK NM for in-vehicle networks. We develop a gateway embedded system and implement a reliable gateway mechanism. We then examine the developed gateway system and present the results of experiments with several trials.