Desiccation in clay soils can result in shrinkage of the soil and subsidence of the ground; this may lead to damage to buildings. As the soil re-hydrates, it can swell, resulting in ground heave; this may also cause damage to buildings. This Digest describes the most commonly used techniques for detecting desiccation and gives guidance on how to use the results of some of these techniques to estimate heave potential. 12 pages.