The costs associated with irrigation pumping, in particular the cost of energy, are assessed in relation to their potential impact on irrigation expansion plans, agricultural economics, and the energy sector. In the Sahel, where the percentage of irrigated agricultural land requiring pumping will range between 90% (Senegal) and 50% (Mali), energy costs will impose restrictions on the depth of pumping, double cropping potential, crop selection, and irrigation system design and management. The case of Senegal is used to compare two systems for powering pumps - direct diesel drive and grid electricity - with regard to fuel use, capital costs, crop selection, and related water requirements. The costs of irrigation pumping (fuel, operations and maintenance, and capital costs) are then discussed more generally; in the case of diesel drive pumps, the impact of pumping costs on crop economics (in particular, rice production) is assessed. An overview of policy issues related to expanding pumped irrigation is presented in conclusion. Appended is an 18-item list of references (1979-85).