Tank irrigation was considered by the Royal Irrigation Department and many foreign missions as the most appropriate answer to the severe water shortage problem in the northeast region of Thailand. In 1975, the Thai government brought the tank irrigation issue to the forefront again by announcing the policy to spread small irrigation tanks throughout the northeast region as soon as possible. The small tanks were built in response to requests from villagers through their tambol councils. Two approaches are used to measure the benefits from the several tank projects. First, benefits are estimated using market based approaches to value agricultural and fish products, and time saved. Second, benefit estimates are obtained through farmer interviews. Total project costs include construction costs, costs of digging the unlined canal, and operation and maintenance costs. The evaluation results, based on market related benefits, are presented in terms of benefit-cost ratios and net present values.