A vast amount of research and development work has been done in recent years to resolve the issues of relevance to the safety of the Liquid Metal cooled Fast Breeder Reactor (lmfbr). Based on the results of this research as well as on the experience gained from the operation of test and prototypelmfbr’s, a certain consensus is emerging on the safety requirements of a modern sodium-cooled large fast power reactor. The paper reviews the fundamental physics and engineering aspects oflmfbr safety with reference to the Fast Breeder Test Reactor (fbtr) now being commissioned at Kalpakkam, and the proposed larger Prototype Fast Breeder Reactor (pfbr). The elements contributing to the inherent safety of fast reactors are recapitulated followed by description of the philosophy of the plant protection system and the use of engineered safeguards to enhance the safety. Finally, the principles used for the containment of radioactivity are discussed.