In order to maintain the biotic integrity and performance of coastal marine ecosystems affected by human population growth and economic development an ecosystem approach to management is required. This is particularly challenging when, as is the case for many coastal ecosystems, development activities on land, often far removed from the coast, have a major impact on the coastal environment. The status of ecosystem management in the U. S. coastal zone is reviewed with a focus on four ecosystems heavily influenced by such landbased activities : the Chesapeake Bay, San Francisco Bay, the Mississippi Delta and Florida Bay. Ecosystem management in these cases requires dfficult decisions among the requirements for development (e. g. fresh water, flood protection, agricultural production, transportation, waste disposal, and building expansion) and environmental conditions in coastal waters. The Chesapeake Bay Program is a large and ambitious effort which is addressing control of diffuse sources of pollutants and the restoration of habitats with the aim of improving water quality and assisting the restoration of living resources. It enjoys strong public support and receives scientific and technical input through modeling and monitoring, yet it is only begiming to approach ecosystem management in a holistic sense. Linking environmental quality with living resources and better managing sprawling population growth in the watershed are vexing challenges. Based on this U. S. experience, science and engineering can make critical contributions toward ecosystem management through sustained investigation, developing clear evidence of the scale and causes of change, forging consensus among diverse technical experts, developing models to guide management actions, and identifying effective and feasible solutions.