This issue of the Highway Research Bulletin focuses on the science of soil stabilization and presents an understanding of the various soils encountered by engineers. The first papers describe soil as a natural body having distinct characteristics inherited from the materials from which it is derived and the environment which produced it. The main body of papers describe our present knowledge of the art and science of stabilization of soils, whether by control of grain-size distribution or by the addition of organic or inorganic compounds to artifically produce or to maintain a stable condition.