[en] The safety and security risk posed by highly radioactive, long-lived sources at the end of their normal use has not been consistently well-managed in previous decades. The Brazilian Cs-137 accident in 1986 and the Thailand Co-60 accident in 2000 are prime examples of the consequences that ensue from the loss of control of highly dangerous sources after their normal use. With the new international emphasis on security of radioactive sources throughout their life cycle, there is now further incentive to address the management of risks posed by legacy, highly dangerous radioactive sources. The ANSTO South-East Asia Regional Security of Radioactive Sources (RSRS) Project has identified, and is addressing, a number of legacy situations that have arisen as a result of inadequate management practices in the past. Specific examples are provided of these legacy situations and the lessons learned for managing the consequent safety and security risk, and for future complete life-cycle management of highly radioactive sources. (author)