To determine whether large-scale irrigation infrastructure projects (IIP) in the Sahel are consistent with the Congressional mandate that A.I.D. projects benefit the poor majority, this report reviews existing IIP's and the Sahel's current irrigation needs in light of the mandate's legislative history. The U.S. Congress, it is argued, is willing in principle to finance large-scale IIP's in the Sahel if it can be shown that no better alternatives exist and that the majority of benefits would accrue to small producers with secure land tenure. IIP's in the Sahel and worldwide, as well as the two largest IIP's in sub-Saharan Africa, in Sudan and Mali, are reviewed to develop a typology of IIP's aiding the poor. Results show that large-scale IIP's are likely to be costly and of scant benefit to the poor if carried out using capital-intensive construction and cultivation techniques (CCT), but that technically and economically viable alternatives exist which would substantially benefit the poor without being socially disruptive. The system envisioned would involve total water control and at least two crops per year, both labor-intensive and mechanized CCT's, traditionally based farmer organizations, and both commercial and food crop production. A review of current irrigation systems and needs for river flow regulation in each Sahelian country and major river basin indicates that the potential for expanding rain fed agriculture and small-scale irrigation - development of which must begin now - is best in Chad, Mali, and Burkina Faso and poorest in Mauritania and Niger, with the Gambia and Senegal holding intermediate positions. It is recommended that A.I.D. help develop the prototype IIP sketched above; promote agricultural development and irrigation in higher rainfall areas of the Sahel and facilitate immigration from those areas to areas with lower rainfall; promote research on marketing for irrigated cash and food crops and on the potential of cash crops for sustaining river basin development programs; train specialists for major river basin development; incorporate primary and secondary cost and benefit analyses into IIP's; and promote the use of a quantified, multi-objective, systems approach to river basin planning. Appendices detail the two surveys mentioned above.