The principles and the establishment of the Danish ground-water monitoring network (67 areas) are outlined. The operation and the protocol of the sampling system are described as is the storage of data in decentralized and centralized systems. The Nyborg monitoring area is used as an example with main limestone and secondary sand aquifers. The first three years' results are evaluated, including an evaluation of the technical function and chemical analyses (inorganics, trace elements and organic micropollutants).