Treatment and disposal options for Department of Energy (DOE) underground storage tank waste at Hanford, Savannah River, Idaho National Engineering and Environmental Laboratory (INEEL), and Oak Ridge National Laboratory (ORNL) are limited by high gamma radiation fields that are produced by high concentrations of cesium in the waste. Treatment methods are needed to remove the cesium from the liquid waste and thus concentrate the cesium into high-activity, remote-handled waste forms. The treated liquids could then be processed and disposed of by more cost-effective means with less radiation exposure to workers. A full-scale demonstration of one cesium removal technology has been conducted at ORNL. This demonstration utilizes a modular, mobile ion-exchange system and existing facilities for the off-gas system, secondary containment, and utilities. The ion-exchange material, crystalline silicotitanate (CST), was chosen on the basis of its effectiveness in laboratory tests. The CST, which was developed through a Cooperative Research and Development Agreement between DOE and private industry, has several advantages over current organic ion-exchange technologies. These advantages include (1) the ability to remove cesium in the presence of high concentrations of potassium, (2) a high affinity for cesium in both alkaline and acidic conditions, (3) physical stability over wide alkaline and acidic ranges, and (4) the elimination of large volumes of secondary waste required for regeneration of organic ion exchangers. Approximately 116,000 L of supernate was processed during the demonstration with similar to 1,142 Ci of Cs-137 removed from the supernate and loaded onto 265L (70 gal) of sorbent. The supernate processed had a high salt content, about 4 M NaNO3, and apH of 12 to 13. This paper discusses the results of the full-scale demonstration and compares these results with data from the laboratory tests.