Project evaluation or project appraisal has experienced a growing interest from both scholars and practitioners in recent years, particularly after the Second World War. This is attributed by Prest and Turvey to the growth of large investment projects and to the expanding role of government in the economic life of most countries. Still more important is the increased interest in planning in developing countries, and the role played by the international financing institutions such as the Interamerican Development Bank, the World Bank, USAID, etc. These agencies, particularly the first two, have had a major impact on the advancement of applied work on project appraisal. Several approaches to project appraisal have been developed from the activities of these agencies, Universities, and particularly water projects in the U.S. It started with cost benefit analysis using market prices; then shadow prices were introduced always with the purpose to maximize the GDP. Lately a distribution or equity objective has been included along with other government objectives. Therefore attempts have been made to develop methodologies that would include these other objectives as well as the growth of GDP. The purpose of the paper is to introduce the basic concepts behind each approach in order to better understand their differences and similarities as well as their practicability.