Field experiments of the lateral resistance of piles driven into a soft clay ground was carried out. The piles were unsupported at the upper side. The following terms were investigated ;
1) the behavior of the laterally loaded piles.
2) the influence of loading condition on the behavior of piles.
3) the influence of loading rate.
4) the lateral ultimate bearing capacity of piles.
　As a result, the same relation between the deflection and the soil reaction as has been ascertained so far, could be approximately adaptable to these piles driven into the soft clay ground.