The Office du Niger is a centrally managed collective irrigation scheme of 55,000 ha. The area is mainly cultivated with flooded rice. As liberalization of commercial activities and restructuring of water management proceeded from the 1980's onward, farmers obtained both increased freedom and responsibilities concerning the production and marketing of their crop. As such, water distribution and maintenance within the tertiary canal level were left to farmers. In combination with an increasing number of farmers per tertiary canal, one would expect coordination of those activities to emerge. Farmers' organization of water distribution and maintenance are diagnosed through a questionnaire survey with 89 farmers on 59 tertiary canals from 5 villages. In only 30% of the cases, clearly defined rules on water distribution exist. In all other cases, a 'first come first serve' rule is applied, though informal consultation between farmers sometimes takes place. With respect to maintenance, decisions on when and how this task should be performed are mostly left to individual farmers. In only 24% of the cases concrete arrangements are made. Moreover, there is often no consensus on rules among farmers, and monitoring and sanctioning mechanisms lack. This results in individualistic behavior causing problems concerning water distribution and maintenance for respectively 20% and 43% of the interviewed farmers. Furthermore, the relations are examined between (i) characteristics of the tertiary canals (infrastructure, total number of farmers and proportion of farmers from outside the village), (ii) types of rules applied, and (iii) occurrence of problems. Results indicate that the type of infrastructure and proportion of farmers from outside the village are related with respectively specific rules for water distribution and maintenance. A strong link exists also between the type of rules used for maintenance and the occurrence of problems, whereas this is not the case for water distr