Ballistic missiles are central to rogue states' strategies to deter and coerce Western democracies in the post-Cold War world. The proliferation of missiles of longer and longer range continues throughout the world, and Australia may come within the range of missiles from North Korea and Iran in the coming decade. Regarding rogue states' ballistic missiles, the United States, Japan and some members of NATO are moving from a posture of deterrence through nuclear punishment to a posture of deterrence through denial. Australia, as a beneficiary of the extended US nuclear deterrent, will have to decide whether to participate in 'extended' US missile defence. Various elements of a ballistic missile defence system, effective against the whole threat spectrum, are under development. The technical limitations of these systems and the importance of the BMD systems architecture (shootlook- shoot capability, layered defence) make it important to define what role Australian BMD systems should play in the overall BMD architecture and what exactly Australia wants to achieve with its BMD systems: defending the Australian homeland against direct or seaborne attack, defence of forward deployed troops or strengthening the US alliance. Each of these missions leads to a different prioritisation of available BMD systems, and no system (for example the SEA 4000 destroyer) will be able to achieve all missions. After looking at the technical aspects of several possible Australian BMD architectures, the paper concludes with recommendations for Australia's BMD policy.