The Supramonte limestone complex, of Jurassic-Cretaceous age, lies within the municipal borders of Urzulei, Oliena and Orgosolo (north-central Sardinia). For the most part, the Supramonte groundwater drains towards the outcrops in the northernmost part of the massif. A minor, almost negligible quantity of water drains towards a series of outcrops along the edge of the carbonate structure, with numerous subaerial and submarine springs. The groundwater in the entire system represents one of the most important water resources in Sardinia, especially for drinking purposes. Taking into consideration the development of karst cavities, permanent groundwater reserves were cautiously estimated to be at least 144 Mm3. Intrinsic vulnerability to pollution has been assessed by means of the EPIK method.