In the field of archaeological geophysics, resistivity and magnetometry are widely used. Both these techniques are well advanced and have been specifically dedicated to archaeological prospecting over the years. Although these methods provide detailed plans of buried remains, British archaeologists are looking increasingly to obtaining depth information. Over the past five years ground penetrating radar (GPR) has been applied to several archaeological sites, with varying degrees of success. Other recent developments include resistance tomography and resistivity pseudo-sections, which can provide approximate depth information. However, seismic refraction surveys have several advantages. First, they provide true depth information giving a profile of buried near-surface layers. Second, processing and interpretation of the data and the form of survey methodology discussed here is relatively straightforward. It must be borne in mind that although this provides detailed information of the interface, unlike the results from a radar survey it is not a continuous profile. Two sites, Coombe Down and Llantrisant Castle were investigated by seismic refraction following the location of ditches by more conventional methods; gradiometry and resistance, respectively. These two sites were chosen because of the believed simplicity of the structures and the clear contrast between ditch fill and host material. At Coombe Down two traverses were undertaken across the large enclosure ditch of an Iron Age enclosure. The infilled moat at Llantrisant Castle was investigated along three traverses by seismic refraction and electrical imaging. Although both surveys were successful in providing information about the respective ditches, the results have highlighted problems with the method and the need for further work.