As the drinking water supply in Denmark is totally based on groundwater, quality monitoring of the groundwater is extremely important to the Danish community Groundwater quality monitoring in Denmark is described in proceedings from the IWA Conference in Buenos Aires (Henriksen and Stockman 1999), GEUS (2002), Stockmarr, Grant and Jorgensen (in press), and in GEUS homepage www.groundwater.dk (English) and www.grundvandsovervaagning.dk (Danish).