A new hydrous crystalline silicotitanate (CST), which we call TAM-5, has be synthesized that selectively removes cesium cations from solutions containing up to 5.7 M Na+ and for a pH range of less than 1 to greater than 14. In basic media and at the high concentrations of Na+ the CST also removes strontium cations from the solution. For a solution containing 5.7 M Na+, 0.6 M OH-, 5.1 M NO3-, 100 mg/L Cs+, and 20 mg/L Sr2+, the distribution coefficients for cesium and strontium are 1000 ml/g and greater than 4,000 ml/g, respectively. For a solution of 5.7 M NaNO3, 100 mg/L Cs+ and 20 mg/L Sr2+ the distribution coefficient for cesium is greater than 10 000 mL/g and for strontium it is equal to 200 mL/g. Experimental studies have also been conducted using complex waste simulants, which compare the performance of this CST and up to 60 other potential ion exchangers/absorbents. These studies substantiate the high selectivity of the CST for cesium in acidic and basic solutions. This new CST, labeled TAM-5, has considerable potential for removing cesium and strontium from defense wastes.