This paper examines the economic determinants and impacts of agricultural research, particularly biotechnology research, with a view to understanding the potential of agricultural biotechnology to address the needs of the poor in developing countries. It surveys public and private agricultural research in developed and developing countries since the green revolution and discusses the public goods nature of much agricultural research. Unlike the research that launched the green revolution, agricultural biotechnology research is primarily being conducted by private firms in industrialized countries to address problems of temperate-zone commercial agriculture. These differences have important implications for the development and diffusion of new technologies to meet the needs of the poor. This paper was prepared as background material for the 2003 issue of The State of Food and Agriculture, which has the theme 'Agricultural Biotechnology: Meeting the Needs of the Poor?' Several companion papers are also available in the ESA Working Paper series.