As a part of the preliminary investigation for the proposed New Tokyo International Air Port, a series of soil test was performed on Kanto loam and Narita sand. Sample of Kanto loam was taken from the Musashino and Shimo-Sueyoshi strata respectively. Index properties and mechanical properties were measured in laboratory. Soil tests on Kanto loam included an investigation of the stabilising effect of adding quick lime. Mechanical properties of Kashima sand were also measured and compared with those of Narita sand. Results of these soil tests gave the data for designing earthworks and also the basis for comparing the quality as a construction material.