"Marine Managed Areas: What, Why, and Where" is a reader-friendly, richly illustrated 16-page booklet that defines MMAs and discusses the challenges of implementation. Based on 5 years of natural and social science research in 23 countries, it is intended to advance discussions among government agencies, non-government organizations, user groups, and other stakeholders about how and why to implement integrated management for the ocean. Marine Managed Areas: What, Why, and Where is a publication of the Science-to-Action partnership, which includes more than 75 organizations led by Conservation International's Marine Management Area Science Program. One approach to the development of better coastal and marine policy and management is the concept of marine managed areas (MMAs). A MMA is an area of ocean, or a combination of land and ocean, where all human activities are managed toward common goals. MMAs are a form of ecosystem-based management, where all elements -- biophysical, human, and institutional -- of a particular system are considered together. There are several overarching principles under which MMAs should be developed: All human uses and their subsequent impacts on the defined area should be considered and their management integrated.Policy and management should be based on the best natural and social science available.All stakeholders in the defined area should be consulted and fully involved in the policy and management development and implementation processes concerning the MMA's conditions and uses. When such principles are fully implemented, the uses of the resources and habitats and the resulting benefits both to the environment and to humans can be optimized.