The widespread residential and industrial use of underground diesel fuel storage tanks, many of which are suspected to leak, is cause for environmental concern. A laboratory study was conducted to examine the effect of in situ hydrogen peroxide treatment on the volume change of soils polluted with diesel fuels. Commercially available hydrogen peroxide offers a short remediation period and can be applied around buildings foundations without any disruption to activities within the building. The problem, however, is that the volume of soil treated with this technology may change, thereby compromising the foundation of buildings. Clean soil samples of clayey silty fine sand were spiked with 2,000 and 5,000 mg of diesel per kg of soil and then compacted to the maximum dry density and placed in consolidometer cells that were filled with varying concentrations of hydrogen peroxide and subjected to 30 kPa pressure for at least 24 hour periods or until no further volume change was detected. Results indicate a nearly instantaneous settlement. Samples treated with higher concentration of peroxide rebounded. The first few hours after inundation showed the greatest volume change. The samples with the highest concentration of hydrogen peroxide expanded the most. The samples that were not spiked but inundated with deionized water showed little volume change. The study confirms that the use of hydrogen peroxide for soil remediation could cause some volumetric change. Below a 15 per cent concentration of hydrogen peroxide, the soil specimens exhibited immediate volume reduction which continued to decrease as concentration increased. It is noted that volume reduction may be associated with decomposition of organic matter, leading to a change in compressibility. 16 refs., 1 tab., 5 figs.