This report examines the recycling of plutonium as thermal mixed-oxide (MOX) fuel in pressurised water reactors (PWRs) in order to discover the number of times plutonium can effectively be recycled. In particular, it describes an exercise based on a realistic, multiple-recycle scenario, which followed plutonium through five generations of recycling in a PWR. It considers both a standard PWR design currently in use and a highly moderated design, in order to provide a better understanding of their relative merits, as well as giving an insight into the limitations of multiple recycling and the long-term toxicity of fission products and actinides.