In order to reduce the concentration of nutrients in surface waters as well as in groundwater, it was decided by the Danish parliament to include restrictions on the use of fertilizers in agriculture, along with a number of other measures taken. It was also decided to set up a monitoring programme on groundwater quality in order to be able to check the effect of various measures taken to protect groundwater against potential pollutants. The monitoring programme has been running for 12 years. However, none of the 600 borings — including 1,100 individual sampling levels — have shown any continuous decrease in nitrate concentration during that period. During 1997 —1998, CFC-age dating was performed on waters from all borings (ca 800) that had tritium above background level — determined by previous measurements in the early 1990s. As expected, a general decrease in nitrate concentrations with groundwater age was observed, although the data were scattered considerably depending on the differences in geology and of land use in the various areas (Stockmarr and Nyegaard 2004).