Abstract : There is an increasing interest in the use of reverberation chambers with mode mixing for testing of electromagnetic susceptibility and immunity of a device under test because of its repeatability and measurement speed. A reverberation chamber is characterized as an environment with uniform, randomly polarized, isotropic fields throughout the volume of the chamber over a large range of frequencies. These chambers are of particular importance because they improve the speed of acquiring shielding and coupling measurements. There have been multiple reports on the use of mode stirred chambers, but they are often inconsistent. The objective is to correlate the characteristics of the reverberation chamber to other facilities currently in use. The US Army Research Laboratory has constructed a medium-sized reverberation chamber (1.75 m x 2.55 m x 4.25 m); its preliminary characterization and calibration are described in this report.