Geographers have always used a variety of physical artefacts e.g. a pluviometer, a map, or a globe as tools to perform their profession. Each of these artefacts has in different ways shaped our ways of being and becoming geographers. Not only have they shaped how we learn but also what we learn. How and with what effect this shaping takes place is not explicit or shared common knowledge but an integrated part of a geographer's experience, and of the professional development of becoming a geographer. New artefacts are constantly introduced into the profession. A major current change is the introduction of Geographical Information Systems (GIS). In this paper we explain and examine the theory of instrumental genesis in order to analyse the interplay between artefacts (such as GIS) and geographical knowledge. Based on a study of first year university students in Denmark we argue that this theory can be used to inform our understanding of the actual and potential roles of GIS in the education of geographers. Our conclusion is that there is a need to recognise GIS as an artefact interwoven with the professional development of becoming a geographer and to start researching the challenges this artefact offers to education and teaching.