DoD systems contain a substantial amount of legacy software that often needs to be evolved or migrated to new hardware and software platforms. This legacy software is important not only because of the large-scale investment it represents, but also because it defines the baseline for describing future desired capabilities and evolutionary growth. The purpose of this report is to provide a set of DoD legacy system migration guidelines. These guidelines are built on lessons learned from actual legacy system migration efforts and they synthesize previous work on the disciplined evolution of legacy systems.