ABSTRACT: The Hungary and Slovakia, which enter in a short time the EU, posses important ground water resources related to the karst areas. Besides the main role of the ground water, which concerns the formation of landscape, is very important the factor of drinking water supply, From this point of view, the most important areas on the territories of both countries are Aggtelek (Aggteleki Nemzeti Park) and Slovak Karst National Parks, which are genetically related on surface or underground by karst phenomena. This is just the water, which is most important for the karst formation, Coming out from the European Union Water Framework Directive, the department of hydrogeology and engineering geology of Miskolc University in the Hungary and the department of geology and mineralogy of the BERG Faculty, Technical University Kosice, have started their cooperation in the field of groundwater protection in the border zone, which consists of important karst areas - Silica Plateau and Dolný Vrch Hill (Alsó Hegy) as well as of Aggtelek karst (Aggteleki karst). The core of the cooperation lies in the use of so called "3E" model (Environmental science, Economics and Ethics) for evaluation of sustainable karst water resources in the studied area.