Laboratory investigation was conducted to study the effects of acidic contamination on compressibility of two natural soils from the Tokyo area. A special container was designed to reproduce in the laboratory conditions the process of long-term soil-water-acid interaction that typically occurs during municipal and industrial waste storage. Solutions of sulfuric acid were used to leach high-quality soil samples for different time periods ranging from 1 to 6 months. The obtained results show that acidic contamination can significantly alter the compressibility of the soil, and the factors determining the degree of such changes are clay mineralogy, soil structure, and the duration of contamination.