Current vehicle electronic control units (ECUs) communicate with each other through networks. Easy integration of these ECUs into a system obviously requires well-standardized network interfaces and corresponding components, which meet the standard properly. One efficient means to ensure that communication interfaces are compliant with the standard is a conformance test standard. As CAN is a widely used communication standard interface in vehicles ISO has worked out a CAN conformance test standard, which is expected to be published as a Draft International Standard - DIS - by end of 1998. This article describes the developing standard, the implementation of a corresponding tester, and how conformance tests are performed. Further, more necessary extensions for more efficient conformance testing with better test coverage are discussed.