The purpose of the High Performance Sederhana Irrigation Systems project (HPSIS) was to build and manage small-scale irrigation systems (less than 2000 hectares) and to test and refine a participatory approach to developing and managing these systems. Because the participatory nature of HPSIS was felt to be "experimental" by the project designers (the Government of Indonesia, USAID and Ford Foundation), HPSIS was monitored extensively. This extensive monitoring enabled the provision of information on problems and the generation of a unique set of data on fanner participation and project performance. As a result, HPSIS provided a seldom-available opportunity to look critically and empirically at a particular application of participatory development, including changes in participation and their expected effects in a relatively large number of sites.