The aim of this abstract is to give a short description of the essential ideas of the Danish national strategy concerning groundwater mapping. Emphasis will be put on a description of the advantages obtained by combining acquirement of spatially dense geophysical data covering large areas with information from an optimum number of new investigation boreholes, existing boreholes, logs and water samples to get an integrated and detailed description of the groundwater resources and their vulnerability (Thomsen et al., 2004). The national mapping project was initiated in 1999. Development of more time efficient and airborne geophysical data acquisition platforms (e.g. SkyTEM) have since then made large-scale mapping even more attractive and affordable in the planning and administration of groundwater resources. The handling and optimized use of huge amounts of geophysical data covering large areas, however has required a comprehensive database, where data can easily be stored, documented, extracted, interpreted, recombined and reused one time after the other. After a hard startup where existing data had to be reported to the new system and efficient software was developed, the database has now become the tool for interpretation, data analysis and data exchange between partners. In the presentation the above mentioned issues with focus on geophysical aspects will be illustrated by examples from different actual mapping projects.