Economists, especially agricultural economists, have undertaken extensive analysis of the gains of technological-based scientific research. This is in stark contrast to the efforts undertaken to understand the economic effects of environmental scientific research. Economic evaluation of environmental science is important because knowledge-based government agencies are regularly required to justify their research expenditure and set clear priorities for their research programmes. This paper addresses the gap in the literature by offering a general framework for evaluating environmental scientific research. The paper is structured around two themes central to appraisals of environmental research: (a) the non-market nature of environmental outcomes; and (b) the pathways to achieve these outcomes. Some of the more important and unique issues addressed include the links between the natural systems being researched, the benefits in terms of resulting goods and services, and their subsequent values, as well as the factors influencing the overall contribution research makes to environmental decision-making.