This book presents the findings and recommendations of the evaluation of the World Bank's Strategic Environmental Assessment (SEA) Pilot Program. It shows that SEA can contribute to improving development policy and sector reform by calling attention to environmental and social priorities, strengthening constituencies, enhancing policy capacities, and improving social accountability. It also provides guidance for undertaking SEA in policy and sector reform. Although it acknowledges the need for tailoring SEA to the context of specific sectors and countries, the book discusses in detail and illustrates with examples the analytical work and participatory processes required for effective SEA at the policy level. It suggests that the time is ripe for scaling up SEA in development policy and sector reform and recommends the establishment of a global alliance on environmental and climate change mainstreaming to support developing countries efforts for achieving sustainable development. The book concludes by arguing that SEA applied to sector reform and development policy is a critical step for these efforts to be successful. This title responds to demand for SEA approaches at the policy level from policymakers, development and environmental specialists of bilateral and multilateral institutions, and environmental assessment specialists. This publication is the result of joint work by the Environment Department of the World Bank, the Environmental Economics Unit at the Department of Economics of the University of Gothenburg (EEU), the Swedish EIA Centre at the Swedish University of Agricultural Sciences, and the Netherlands Commission for Environmental Assessment (NCEA.) In line with the Paris Declaration on Aid Effectiveness, the book also contributes to harmonization of SEA approaches by the donor community that is led by the SEA Task Team of the OECD Development Assistance Committee.