Current trend in the stress strain analysis of the structure-geomaterial interaction is to use discrete element models, frecuently using finite element techniques. However, it is still common practice to use the Winkler hypothesis where simplicity of the calculation wants to be kept, since it allows for soil structure interaction analysis. This paper describes the most common methods to determine the coefficient of subgrade reaction, known as kS of Winkler as well. The effect of compositional and environmental factors on kS is illustrated, including examples of tropical residual soils.