Socioeconomic problems facing irrigation planners and managers are examined in this review of the literature on irrigation in India, Pakistan, Thailand, and Egypt. Focus is on three critical areas: water allocation; institutional arrangements for irrigation management; and investment alternatives. Section I, on water allocation, reviews research on a variety of issues, e.g., allocation of water over time and among users; conjunctive use of groundwater and surface water; system size; means of reducing water loss; the impact of allocation procedures on waterlogging and salinity; and differing perceptions of farmers and irrigation managers. This last issue - the need to make individual and societal incentives compatible - recurs in Section II on institutional arrangements. Other institutional issues include: coordinating government involvement; financing water user associations; farmer participation; and the role of land tenure and water rights. Section III discusses two key investment questions - new projects vs. rehabilitation and small projects vs. large ones. Topics here include: frequency and type of maintenance and rehabilitation; preventing overuse of groundwater; communal- vs. government-operated systems; tank projects; the relationship between socioeconomic problems and system size; water application intensity; and drainage and terminal infrastructure.