Distribution coefficients of cesium on natural and cation-enriched (Na+, K+, NH4+ and Ca+2) forms of clinoptilolite were measured by batch, radioactive tracer technique. The measurements were carried out for an initial cesium concentration range of 10(-6)-10(-1) mol/dm(3) and at temperatures of 25, 40, 60 and 80 degreesC. Experimental isotherms evaluated from distribution coefficients were fit to Langmuir, Freundlich and Dubinin-Radushkevich (D-R)models. Of the models tested, D-R model was found to represent the isotherms better in a wider range of concentrations than either Langmuir or Freundlich model. Breakthrough behavior of cesium on natural and cation-enriched forms of clinoptilolite for a particular set of conditions were also determined in a small size column. Column parameters were evaluated using mass transfer zone concept. (C) 2002 Elsevier Science B.V. All rights reserved.