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Abstract  Hydrogeological and geophysical surveys confirm that the aquifers of the Capoterra plain in Sardinia (Italy) constitute a complex, multilayer system. In the north-east of the plain, this system is composed of a shallow aquifer of recent alluvium and a deeper aquifer separated from the former by a clay layer; in the south-west there is no separation between the two aquifers. The deepest and most important member of the multilayer aquifer system is situated at the transition from Quaternary to Miocene sediments. With respect to deep structures and stratigraphy, several differentiations inside the Miocene sedimentary filling, whose overall thickness is in the order of 300 m, have been found. The combined interpretation of several datasets allows the Capoterra plain to be reliably modelled from surface to a depth of several hundreds of metres and provides the possibility of finding deeper groundwater resources. Concerning the latter, since Miocene materials are known to be impermeable in the middle of the plain, in contrast to the aquifers hosted in the Quaternary sediments and alluvium, the probability of finding fresh water at a depth of less than 350–400 m is very low. The condition of seawater intrusion affecting the aquifers is also elucidated. [ABSTRACT FROM AUTHOR]