The range of EM instruments manufactured by Geonics Ltd, Canada, has been used predominantly in North America, particularly eastern Canada, and now increasingly in Europe. There have been some major developments in the portability and ease of use of some instruments and their ensuing popularity has resulted in the techniques being used more widely. The interpretation methods available are largely dependent upon the instrumentation used for each survey and the information about the plethora of equipment available is widely scattered throughout the literature.