The paper is divided into four main parts, the first dealing with the soil and its clay fraction in particular. The make-up of clays is explained, as well as the phenomena of electric surface charges, adsorption, base exchange, etc. Methods of determining clay types are mentioned. The second part deals with the lime. The chemical composition of some typical limes are given and phenomena such as hydraulicity, plasticity and soundness are mentioned. Extracts from tentative specifications for Toad limes are given. The third part deals with the reactions which take place in a soil by lime stabilization. The most important reactions are base exchange and cementive action. Some practical considerations concerning construction work are mentioned. The fourth and last part of the paper gives some examples of lime-stabilization works in the Transvaal.