MOX fuel, a mixture of weapon-grade plutonium and natural or depleted uranium, may be used to deplete a portion of the world's surplus of weapon-grade plutonium. A number of reactors currently operate in Europe with one-third MOX cores, and others are scheduled to begin using MOX fuels in both Europe and Japan in the near future. While Russia has laboratory-scale MOX fabrication facilities, the technology remains under study. No fuels containing plutonium are used in the US The 25 presentations in this book give an overview of MOX technology.