SuperLigŇ 644 ion exchange resin is currently being evaluated for cesium (137Cs) removal from radioactive Hanford tank wastes. To assess the performace of the resin in column configuration, a multiple batch contact method was used to determine the equilibrium distribution coefficients (Kd) and percent removal for 137Cs from highly alkaline waste solutions obtained from the Hanford Site. The equilibrium loading data were interpreted in terms of Freundlich and Dublin-Radushkevics (D-R) isotherms. The equations fit the experimental data remarkably well considering the complexity of the Hanford tank waste compositions. The mean energy of adsorption and total resin capacity were calculated. The mean free energy for adsorption of cesium from Hanford tanks was ~9 kJ/mol. The total exchange capacity of the SuperLigŇ 644 resin ranged from 0.72 to 3.46 mmole/g resin, depending on the Hanford tank composition. The Kd results reveal that SuperLigŇ 644 resin in highly selective for cesium in the presence of relatively high concentrations of sodium and potassium salts.