In response to recommendations by the 1971 Geneva Conference and in compliance with a resolution by the IAEA General Conference to intensify efforts to assist developing countries in planning their nuclear power programmes, the Agency has performed a number of general as well as country-specific studies in co-operation with Member States. To be able to evaluate the order of magnitude of the economic potential of nuclear power in developing countries, the Agency carried out a Market Survey in fourteen selected countries. This survey was completed in 1973 and has been summarized in IAEA Bulletin, Volume 15, Number 5. After the quadrupling of oil prices in late 1973 it became obvious that nuclear power will have vital importance for covering an increasing portion of the electric energy demand of many developing countries in the coming decades, both for economic and diversification reasons and to secure an energy supply. In order to extend the scope of the Market Survey and to incorporate the effects of changes in fossil and nuclear energy economics, it was updated in 1974 and extended to all countries eligible to receive technical assistance under the United Nations Development Programme. Parallel to this necessarily theoretical approach, a number of in-depth studies were performed to assist the nuclear power planning activities of Member States. The methodology and results of these studies are summarized. (author)