Growing population and rising levels of economic activities increase human demand for water and related services. In the past large dams have often been seen as an effective way of meeting water and energy needs. However, a global review recently carried out by the World Commission on Dams has emphasized the wide range of problems associated with dams, making it more difficult to finance large dams. This paper deals with the role of dams in development. The need for dams, the purpose of large-dam building, major benefits and social and environmental considerations are dealt with. As a case study, the contribution of dams to Turkey's economy is described.