With an installed geothermal electric capacity of 853 MWe, Mexico is currently the third largest producer of geothermal power worldwide, after the USA and the Philippines. There are four geothermal fields now under exploitation: Cerro Prieto, Los Azufres, Los Humeros and Las Tres Virgenes. Cerro Prieto is the second largest field in the world, with 720 MWe and 138 production wells in operation; sedimentary (sandstone) rocks host its geothermal fluids. Los Azufres (88 MWe), Los Humeros (35 MWe) and Las Tres Virgenes (10 MWe)are volcanic fields, with fluids hosted by volcanic (andesites) and intrusive (granodiorite) rocks. Four additional units, 25 MW, each, are under construction in Los Azufres and due to go into operation in April 2003. One small (300 kW) binary-cycle unit is operating in Maguarichi, a small village in an isolated area with no link to the national grid. The geothermal power installed in Mexico represents 2% of the total installed electric capacity, but the electricity generated from geothermal accounts for almost 3% of the national total. (C) 2003 CNR. Published by Elsevier Ltd. All rights reserved.