Following recent advances in the field of colloid science, a working hypothesis aimed at describing the make-up of stable soil structures has been developed and is described. In the light of this hypothesis, the mechanism of shear failure in soils and their response to long-term sustained and repeated loads has been studied. A phenomenon which has been observed in the laboratory and is termed step-strain behavior is reported, and a possible explanation of this phenomenon in terms of soil structure is presented. Finally, an experimental investigation aimed at evaluating some of the predictions of the theory with respect to creep behavior and ultimate strength is described.