Pore parameters of cement-stabilized soil samples were obtained by a mercury intrusion test to allow evaluation of the influence of microstructural characteristics on the macromechanical properties. Samples were subjected to a range of unconfined stresses (fractions of their unconfined compressive strength). Five characteristic pore size classes were determined (larger than 40 μm, 40–2.5 μm, 2.5–0.4 μm, 0.4–0.04 μm and less than 0.04 μm) and changes in the relative proportions of these classes were used to evaluate structural changes and the development of progressive failure of the cement-stabilized soils. The results show that in this cement-stabilized soil changes in applied stress have a significant effect on variations in micropore content. No obvious changes were observed in the proportions of larger pores during the initial loading stage. However, these proportions changed significantly as failure approached. The porosity of the samples showed a tendency to increase (dilatancy) after an initial decline.