Abstract Surface geoelectrical methods are currently used in solving a range of hydrogeological problems involving both quality and quantity issues. This is the first of two papers devoted to the use of applied geophysics in solving problems of groundwater protection and pollution detection. In this paper, attention is focused on the fundamental principles of geophysical surveying for pollution and protection studies. Geoelectrical methods, in particular resistivity methods, which are the most widely applicable geophysical method, are analysed in detail. Relations between geoelectrical and hydrogeological parameters are discussed with a view to groundwater pollution, as well as methods of measurements and the principles of geophysical and hydrogeological interpretation of results. Several examples are given to illustrate the principles. A future paper will be devoted to presentation of case histories.