Along with the recent success of economic growth in the developing world comes more pollution. Reducing these emissions while still enabling these countries to grow requires the use of new technologies in these countries. In most cases, these technologies are first created in high-income countries. Thus, the challenge for environmental policy is to encourage the transfer of these environmentally-friendly technologies to the developing world. This paper reviews the economic literature on both the creation and transfer of environmental technologies, with an emphasis on how the development of new technologies in leading economies can lead to environmental improvements in developing countries. I begin by discussing the incentives for environmentally-friendly innovation, which occurs primarily in developed countries. I then review the literature on the transfer of these technologies to the developing world. A key point is that technology diffusion is gradual. Early adoption of policy by developed countries leads to the development of new technologies that make it easier for developing countries to reduce pollution as well. Globalization also plays an important role in moving clean technologies to developing countries. Since clean technologies are first developed in the world’s leading economies, international trade and foreign investments provide access to these technologies. Finally, the absorptive capacity of nations is important. The technological skills of the local workforce enable a country to learn from, and build upon, technologies brought in from abroad. I conclude by discussing the implication of these lessons for policy, focusing on three examples pertaining to climate change: the Clean Development Mechanism, the role of intellectual property, and government-sponsored R&D.