In this work we make a first, partial, assessment of the low- to medium-temperature geothermal reserves of Mexico. The assessment covers about 30% of the identified geothermal surface manifestations. For reserve assessment we use the volume method, supplemented by Montecarlo simulations and statistics, in order to quantify the inherent uncertainties. We estimate these reserves as lying between 7.7 x 10(16) and 8.6 x 10(16) kJ, with 90% confidence. The distribution of most likely reservoir temperatures is in the 60-180 degreesC range, with a mean of 111 degreesC. These massive amounts of recoverable energy and the associated temperatures are potentially important for the economic development of the associated geothermal localities. (C) 2003 CNR. Published by Elsevier Ltd. All rights reserved.