The chapter presents an overview of the geology, classification, and distribution and swelling potential of expansive soils and rocks from the Arabian Gulf country of Oman. After a description of the geological setting of case study area, the origin and types of soils and rocks encountered in areas of building damage were identified. A typical soil/rock profile at an area with a known expansive soil problem, describing the expansive materials was presented. Using an empirical relationship, data from 56 construction sites was employed to classify broadly the likely swelling potential of the regional soils. Maps showing the geographical distribution of expansive soils and rocks, their swelling potential, and the geology of the regions were developed. These maps were based on information from soil laboratory tests, reported occurrences, and local geological conditions.