This paper presents the results of the monitored performance of a reinforced concrete diaphragm wall (slurry wall) while making a seven-level, 24.4 m (80 ft) deep excavation in downtown Boston for the construction of an underground garage using the “top-down” construction technique. In developing the design and construction methodology, ground movement control was considered to be an important aspect in design of the excavation support system. Finite element analyses were performed to model the anticipated soil and adjacent building movements. Observed movements during construction were compared to the values generated during design to judge the performance of the excavation support system. Modifications to the construction sequence were made to help reduce future movements. The owner's commitment of resources necessary to support the program played an important role in achieving the desired goals.