The Philippines' National Irrigation Administration (NIA) of the Philippines has piloted and implemented several approaches to organizing farmers to undertake management responsibilities for the operation and maintenance (O&M) of irrigation systems. in 1983, NIA piloted a new approach which, instead of following the earlier practice of employing professional community organizers who were college graduates, employed farmers to organize co-farmers into Irrigators' Associations. The Farmer Irrigators' Organizing Project (FIOP) was piloted in a Pump Irrigation System of the Angat-Maasim Rivers Irrigation System, one of the oldest and largest irrigation systems administered by NIA. The system serves an area of 31,485 ha and is located approximately 53 km north of Manila. The implementation of FIOP, which employed selected and well-trained farmers in organizing co-farmers, yielded several positive results. The activities of FIOP resulted in active Irrigators' Associations at field and distribution levels, reduced O&M costs, enabled higher fee collection rates, and made water distribution more equitable. Compared to previous approaches with professional organizers, this new approach showed that organizing activities can be shortened, made less expensive, and be very effective. The encouraging results of the pilot implementation of FIOP led to its nationwide implementation in all National Irrigation Systems being operated by NIA. This case study shows that rehabilitation and institutional development must go together. Also, the personal manner of sociality, character, camaraderie, and cooperative decision making of the implementers played an important role in the success of the implementation of the Farmer Irrigators' Organizing Project. (Author abstract)