The Cerro Prieto field of northern Mexico is the largest water-dominated geothermal field under commercial production at the present time. In 2000 more than 115 million tons of fluids were extracted, but only about 20% was injected back into the reservoirs. This deficit has contributed to a drop in pressures resulting in localized boiling, influx of cooler groundwater and other reservoir processes. The influence of geologic features, especially faults, on these processes and on the response of different parts of the field to production is described. The study illustrates the importance of a multidisciplinary approach to gain an understanding of the behavior of geothermal systems under production. (C) 2003 CNR. Published by Elsevier Ltd. All rights reserved.