The existence of an important infrastructure stock with extended usage periods that has suffered damage or collapse under conditions of normal functioning or external actions that are slightly higher than normal has raised the interest of the scientific community for the development of a structural health monitoring technique. It has been identified that the variation of these dynamic parameters depends mainly on the mass and stiffness of the structure. However, it has been observed recently that temperature, rain and wind also affect the dynamic parameters of the system. In practice, it is difficult to determine if the observed changes in these parameters are caused only due to structural effects, or also due to climatic changes. This article presents results of a study conducted to investigate the effect of soil water content in the natural frequency of a scale soil-structure system. © 2009 IOS Press.