As the complexity of communication networks increase, it becomes increasingly more difficult to isolate and diagnose network faults. This maintenance problem is due to the large number of functional elements within the networks, the elements' technical complexity, and their inherent interaction. One technique to solve this problem is to use expert system technology to manage the vast amount of status information produced by these networks and to provide an automated diagnostic reasoning about the location and cause of observed faults. In this thesis, a prototype expert system based diagnostic tool for cable trunk amplifier networks is presented. This tool is capable of isolating and diagnosing the most common network level faults which occur in these type of networks. This tool was created as a proof-of-principle of the use of expert system based diagnostic tools on this type of communication network. As such, the tool was tested on a series of network faults occurring within the Rogers Cable Television Victoria cable trunk amplifier network. The results of these tests are presented.