There are many mthods to evaluate the resistance effect of the piles against the slides in the ground. This paper describes examining the method proposed by Kitajima and Kishi by means of laboratory test and theoretical analysis by finite element method (F.E M.). The lateral forces acting on the piles are calculated by measured values of bending strains occured in the model piles. The values of these lateral forces roughly agreed with measured values by oil-pressure gauges equipped with the test vessel. Therefore Kitajima and Kishi's method is endorsed experimentally.
　Through the theoretical analyses by F.E.M.,a value of coefficient of subgrade reaction depends on the interval between the piles and has a great influence on lateral displacements or sectional forces occured in the piles. However, Kitajima and kishi's method considers only the resistance effect as single pile, so there is a certain limit to use this method practically. The authers think that this method is theoretically proper, however, determining the lateral forces, the value of coefficient of subgrade reaction, and so on in practical pile designs will be studied further.