This handbook, an updated version of the original “Layman’s Handbook on how to develop a Small Hydro Site, published by the Commission in 1993, has been written, in the frame of the ALTENER programme, under contract with the Commission of the European Communities (Directorate General for Energy, DG XVII). It has not been designed to replace professional expertise but it is hoped it is comprehensive enough to advise laymen on all necessary procedures that should be followed to develop a site. However its content includes enough technical information, so a non-specialist engineer would be able to produce a primary feasibility report.