A generalized engineering classification method for characterizing Pleistocene glacial materials on the basis of their glaciological mode of origin is presented in this thesis. In formulating the classification an interdisciplinary approach has been adopted. The geotechnical aspects have been based largely on data from extensive site investigations undertaken at the Brenig dam site in North Wales, supplemented where necessary by data obtained from the glaciological and geotechnical literature. Particular attention has been paid to the macrofabric of the deposits in view of the controlling influence that discontinuities exert on engineering behaviour. The glaciological appraisal of the materials has also relied heavily on detailed evaluation of the engineering behaviour and textural properties of the Brenig deposits. However, in order to extend the applicability of the proposed classification to other locations, the site-specific data has been correlated with results from current glaciological research on modern arctic and temperate glaciers. As a prerequisite for such an assessment, a reconstruction of the glacial history of the Brenig site has been attempted. The similar mineralogy of the various glacial deposits and the availability of extensive geotechnical data on the complete suite of materials has made the, site ideal for this purpose. In presenting the results of the studies, the thesis has been divided into four sections. By way of background, in Part I the methodology and scope of the investigations conducted at Brenig are presented. In Part II a comparison is made between the characteristics of Recent glacial deposits and the Pleistocene materials at Brenig. The stratigraphy and glacial chronology of the site are developed in Part III, while in Part IV the geotechnical evaluation of the site is presented and set within the glaciological framework as a basis for the proposed classification.