A field instrumentation and monitoring study on a 52-ft (15.8-m) high mechanically stabilized earth wall was undertaken. The field monitoring program was carried out on different sections along the wall, representing three different wall heights and two geometries. Monitoring results pertaining to reinforcement working forces, earth pressures at the base of the reinforced soils, and wall deformations are presented. The magnitudes and locations of maximum axial forces measured in the reinforcement are discussed and compared with the predictions by the method adopted by the Federal Highway Administration (FHWA) and the load and resistance factor design (LRFD) method. Comparisons between the field measurements and the design methods for the tallest section with straight backfill (simple geometry) indicated that the LRFD method predicted the reinforcement forces more closely than the FHWA-adopted method. However, both methods failed to predict the locations and magnitudes of the maximum axial forces that developed in the reinforcement at the wing-wall section (sections with three-dimensional sloping backfill). The geometry of the wall and backfill, the type of wall-facing panels, and the interpanel connections appear to influence the deformation and settlement response of the reinforced earth wall. From the measured reinforcement wall connection forces, it was determined that the connection forces depended on the depth of embedment and the shape of the line of limiting equilibrium. The vertical pressure measurements deviated from those predictions by the three methods: Meyerhof, trapezoidal, and uniform distribution. These discrepancies are attributed to the lack of knowledge of the influences of the wall-facing element and the frictional stresses that may have developed along the interface between the retained soil and the reinforced soil mass.