Rational methods for setting priorities for maintenance of irrigation systems are developed. The methods, which are aimed for use by irrigation system managers, describe the link between maintenance activities and the consequent improvement in the performance of an irrigation system. Hydraulic analysis methods are developed for assessing potential 'restorative maintenance' tasks, which are usually undertaken to increase the deliveries of water to the outlets. The new methods use inputs that have been limited to those easily available from scheme records, the knowledge of irrigation agency staff and from infrastructure inspections. Two alternative methods are developed, one based on Fuzzy Logic and one on numerical modelling. Risk analysis methods are also developed for assessing 'preventative maintenance', to reduce the probability of supply failures. Benefit-cost ratios are derived that allow direct comparison between maintenance tasks of each type. The methods are tested at two irrigation systems in Tamil Nadu, India.