This Safety Guide provides specific recommendations on the safety of uranium and plutonium mixed oxide (MOX) fuel fabrication facilities. The potential hazards of a MOX fuel fabrication facility are release of actinides, increased radiotoxicity due to trans-uranium actinides, and nuclear criticality. The toxicity of plutonium is high and therefore it is important that best practices be employed at all stages of the fabrication of MOX fuel, and that plutonium be handled, processed, treated and stored safely. The revised Safety Guide reflects current operational practices at MOX fuel fabrication facilities. The recommendations in this publication are aimed primarily at the operating organizations of fuel fabrication facilities, regulatory bodies and designers.