Abstract: Schmertmann's method for estimating the settlement of sandy soil stratum is considerable simple and more reliable. The essential problem is how to evaluate the modulus of elasticity to be used in calculation. There are three sources from which we can get various information concerning this parameter, i. e. （ 1 ）from subjective judgment of the qualified engineer or judgment based on the data and experience with the soil in the neighborhood, （2） from appropriate empirical equations derived from the regression analysis, such as linear empirical correlation between the mean modulus of elasticity and static cone penetration resistance, and （ 3 ） from in-situ measurement carried out specially for the project, such as loading test, pressuremeter test, etc. In the use of Bayes' theorem, we can combine and update all of those gathered information. This would lead to a more accurate estimation of design parameter. Furthermore, probabilistic procedure is recommended to evaluate the confidence interval for the actual settlement corresponding to specified reliability for the case where the soil parameter is normally distributed. Finally, an illustrative example is included in the last part of this paper.