Plant data systems are emerging as a critical plant support system technology. In particular, plant-wide Historical Data Systems (HDS) are pivotal to the successful implementation of technical surveillance and analysis programs supporting plant operations, maintenance, safety, and licensing activities. In partnership with Canadian CANDU utility and design organizations, AECL has conducted a review of current Canadian CANDU HDS approaches with emphasis on understanding the existing functionality and uses of plant historical data systems, their future needs and benefits. The results is a vision of a plant-wide HDS providing seamless access to both near real-time and historical data, user tool-kits for data visualization and analysis, and data management of the large volume of data acquired during the life of a plant. The successful implementation of the HDS vision will lead to higher capability and capacity factors while minimizing Operations, Maintenance, and Administration (OM and A) costs. (author). 5 refs, 3 figs.