This paper introduces the resistance of the ground (soil resistivity) and measurements of the soil resistivity. It is well known that the resistance of the ground electrode is heavily influenced by the soil resistivity in which it is driven and as such, measurements of the soil resistivity are an important parameter when designing grounding installations. Knowledge of the soil resistivity at the intended site, and how this varies with parameters such as moisture content, temperature and depth, provides a valuable insight into how the desired ground resistance value can be achieved and maintained over the life of the installation with the minimum cost and effort.