The effective utilization of geothermal energy is dependent on a knowledge of the total amount and character of the heat available in a particular geothermal field. The development of a conceptual model of a hydrothermal resource is essential for estimating its value and the proper mode of exploitation. This paper describes results of studies leading to the construction of a model for the Los Azufres (Mexico) hydrothermal system. The geometry of the system is found to correspond to a dome-shaped structure, distorted by two columnar zones of natural fluid discharge, which give rise to two areas of surface manifestations. A vertical progression is observed, from a hot liquid phase at depth to an intermediate two-phase liquid-dominated zone, and then to a relatively shallow two-phase vapour-dominated zone.