The methodology used to assess the historical reliability performance of a Canadian Utility's electric distribution system is outlined. Included is an overview of the process used to collect and organize the required interruption data as well as a description of the performance indices calculated for use in the causal assessment. The various component parts of the reliability performance assessment are described. This includes a description of indices comparison between years and to the average at different levels of the system and by outage cause and component failure. Finally, results from the 2004 reliability assessment of the utility's electric distribution system are summarized and the application of the calculated performance statistics in planning, operating and maintaining distribution systems is described.