The world is becoming more and more demanding in the quality of life of the common citizen. One way to achieve this quality is to enjoy health tourism. Medical Spa are an excellent equipment in this sense, because they allow practices of health treatment, or relaxation and well-being, aqualudic, focused on the use of natural mineral water, and with direct or indirect monitoring of health professionals (doctors). Thus, in Portugal, for a medical spa to function as such, it must have mineral water of stable quality. For this to be possible, it is necessary to comply with a set of procedures in the exploitation of water, and to impose restrictions on certain types of activities and due limitations on the occupation of the territory, in accordance with the implementation of the Protection Perimeter of groundwater abstraction of the medical spas. The maps of vulnerability to groundwater contamination are excellent instruments to contribute in the elaboration of the aforementioned Protection Perimeter. Thus, this paper presents the fundamental hydro-environmental elements in order to present the vulnerability map of the São Tiago medical spa territory. The General DRASTIC method is used, with a set of adaptations, called Specific DRASTIC, in order to preserve the areas most sensitive to the potential contamination of natural mineral water, and to liberate other areas that are not of potential danger to its contamination. It is also presented the map of occupation of the territory with registration of the main sources of potential pollution, making an analysis of the relationship between the results of the vulnerability map and the types of occupation. Finally, some conclusions are briefly presented.