The reduction of transmitted lateral swelling pressures on retaining structures constructed in expansive soils is investigated. Swelling pressures will develop if the soil is not allowed to swell freely. The magnitude of swelling pressure depends on the degree of expansion permitted. When a little soil expansion is allowed, the swelling pressure may be decreased considerably relative to the case of no expansion. This study examines the role of expanded polystyrene (EPS) geofoam in accommodating soil expansion and hence reducing swelling pressures on adjacent structures. Several hypothetical cases are presented whereby reductions on the transmitted lateral pressures due to expansive soils are examined for different thickness of EPS geofoam. (c) 2007 Elsevier Ltd. All rights reserved.