A retaining wall is subject to various limit states such as sliding, overturning and bearing capacity, and it can fail by anyone of them. Since a great deal of uncertainty is involved in the analysis of the limit states, the use of detenninistic conventional safety factors may produce a misleading result. The main objective of this study is to develop a procedure for the optimum design of a retaining wall by using the reliability theory. Typical gravity retaining walls with four different heights were selected in this study. The walls were designed first to satisfy the conventional design criteria, and later the safety indices inherent in the walls were computed by using Advanced First Order Second Moment method. With the safety indices the probabilities of failure for the three limit states were calculated and the probabilistically optimized design could be achieved by using the probability of failure. The influence of the coefficient of variation on the probability of failure was investigated. The ratios of base width to wall height which lead to the optimum design were obtained through a parametric study. / Ph. D.