This paper surveys the existing empirical evidence on the unintended consequences of food aid. Micro-level evidence is presented on the impacts of food aid deliveries on household labour supply, production incentives, consumption patterns and natural resource use. At the meso-level, evidence on the impact of food aid on market development, market prices, informal insurance arrangements, and the behavior of implementing agencies is surveyed. Macro level evidence on the impact of food aid on balance of payments, economic growth, international trade, exchange rates and other factors is reviewed. Although food aid can have negative unintended consequences, the empirical evidence is thin and often contradictory. The available evidence suggests that harmful effects are most likely to occur when food aid arrives or is purchased at the wrong time, when food aid distribution is not well targeted to the most food insecure households, and when the local market is relatively poorly integrated with broader national, regional and global markets. These results imply the need for caution in basing food aid programming decisions on a relatively weak body of empirical evidence.