The Dinaric system (Dinarides) is a long, NW-SE oriented orogenic belt, parallel to the Adriatic Sea with numerous intermountain depressions, large karst poljes and valleys created by numerous perennial or sinking streams. Its NW fringe is the Crasso area around Trieste in Italy while the SW part extends deep into Albania. The Dinaric region is a karst holotype. The term karst was born in this region, as well as karstology - a new scientific discipline whose foundations were laid by Jovan Cvijić and his peers at the end of the 19 Century. In the region, it is distinguished between three major tectonic units: External (closest to the Adriatic Sea), Central and Inner Dinarides. The main sedimentation cycle in the Mediterranean geosyncline (Tethys) started in the Permian and lasted through Upper Cretaceous. All the classic karstic features are developed; for example, there are more than 150 poljes and in certain areas a number of dolines reach up to 150/km2. The average infiltration rate is 60% of precipitation. There are 230 springs with a minimal discharge of over 100 l/s, while about 100 springs have a minimal discharge of over 500 l/s. Concerning karstic water resources, the Dinaric region is by far the richest in all of Europe: in southern Montenegro the average specific yield is 40 l/s/km2. Nevertheless, there are numerous obstacles to sustainable groundwater utilization; first of all the huge annual variation of discharges and the vulnerability of aquifers to pollution. The rise of several new sovereign states from what was once Yugoslavia created complex transboundary inter-linkages that impact on the use of shared water resources for domestic supply, power generation and agriculture. DIKTAS (Protection and Sustainable Use of the Dinaric Karst Transboundary Aquifer System) is an on-going GEF project implemented by UNDP and UNESCO‘s IHP, initiated to improve the understanding of shared water resources and to facilitate their equitable and sustainable utilization, including the protection of dependent ecosystems. Within the project, a regional hydrogeological characterization is carried out and seven transboundary aquifers are currently assessed in more detail in order to establish a common scientific understanding and an information system for the monitoring and management thereof. Five of them are set along the borders of Croatia and Bosnia and Herzegovina (B & H), one is between B & H and Montenegro and one is shared by Montenegro and Albania.