The classical use of 0.3 for the static coefficient of friction for sheet pile interlocks was investigated in this study. The effects of cyclic displacements on the coefficient of friction of the interlocks was also examined. A broad range of values for the coefficient of friction was observed for over 2000 observations of the shear force required to initiate interlock displacement. The mean observed value of the coefficient of friction was greater than 0.3 for low interlock stress. The mean coefficient of friction decreased with increased interlock stress. At interlock loads of five kips per inch the mean coefficient of friction was approximately equal to 0.3. The relationship between interlock stress and the coefficient of friction was found to be nonlinear. An exponential model to predict the coefficient of friction for interlock loads between 1 and 5 kips per inch was developed. To study the effects of cyclic displacements on interlock friction the specimen interlocks were displaced approximately one hundred times. No significant effect on interlock friction was observed. / M.S.