Abstract Geothermal exploration in Chile started in 1968 as a result of a project subscribed by the Chilean Government and the United Nations Development Program. This project is being administrated by the Corporación de Fomento de la Producción together with the United Nations (CORFO/UNDP). The purpose of this project is to determine the geothermal possibilities of an area of 108,000 km 2 in the high Andes of Tarapacá and Antofagasta provinces approximately between 18° and 25°S lat. and east of 69°30'W long. The first stage of geothermal investigations has been restricted to the northernmost part of the country mainly because this region possesses no other energy resources. Limited hydroelectric resources have already been totally developed, and oil exploration has not been successful. Although there was some previous geothermal exploration in the area, this paper is based on the writer's experience from 1968 to 1973 while in charge of the project's research in Tarapacá and Antofagasta provinces. Many of the results presented were obtained by a team of geologists working in this project, in which J. Healy, of the New Zealand Geological Survey, had a very important part.