Abstract: Improving the behaviour of soft clays using lime or cement is not new. The studies report the high swelling failures in lime and cement-stabilized clays due to the formation of swelling minerals such as ettringite. The formation of needle-shaped ettringite in the stabilized materials can be identified using the X-ray diffraction (XRD) and the scanning electron microscopy (SEM). The earlier studies on the influence of ettringite upon the lime and cement-stabilized clays are reviewed and the factors influencing ettringite formation are examined. The results indicate that the formation of ettringite has both pros and cons in lime and cement-stabilized clays, and it is a complex phenomenon influenced by several factors.