ABSTRACT: Multilateral project of European hydrogeologists - COST Action 620 "Vulnerability and risk mapping for the protection of carbonate (karst) aquifers" - stared its activity in 1997 as a scientific programme supported by the European Commission, with the ambition to elaborate common, generally consistent methodology of groundwater vulnerability assessment in karstic areas. Slovak hydrogeologists could have participated as well, and brought their views into the scientific discussion. COST action 620 finished in 2003 with the final report, and the elaborated product can be cali ed "a European approach" more than a methodology. However, this approach can be applied not only to the karst rock media, but - taking into account the "flow concentration factor" - also to all kinds of rock environments. Another resuIt of this project was the establishing of generally acceptable definitions of "groundwater vulnerability", "intrinsic and specific vulnerability", "source and resource vulnerability", "hazard" and "risk" terms, which were born after long-lasting, ever returning discussions throughout the several years of the Action COST 620 meetings. The aim of this paper is to spread these achievements into the Slovak hydrogeological audience and to keep its traditional approaches in touch with today's European hydrogeological conceptions.