​The excellent behavior of reinforced soil retaining walls under a wide range of site conditions has given designers using conventional design assumptions little cause for concern regarding the effects of either the foundation soil or the retained fill supported.by the wall [Fig. 1(a)]. In the meantime, analytical and 1-g experimental studies on the effect of foundation conditions on wall behavior have produced contradictory conclusions. This research examined experimentally the effect of foundation soil and retained fill on wall behavior. The primary technique used in the study was centrifuge modeling, first applied to reinforced soil walls by Bolton et al. (1978).