A novel extraction chromatographic resin for the separation and preconcentration of cesium from acidic nitrate media comprising an inert polymeric substrate impregnated with 1,3-calix[4]bis-o-benzo-crown-6 ("BC6B) in a chlorinated diluent is described. Cesiam is shown to be both strongly and selectively retained by the resin at low (< 1m) . Only potassium ion (at concentrations exceeding ca. 0.01 M) exerts a significant adverse impact on cesium retention. Unexpectedly, cesium uptake by the resin does not exhibit the acid dependency anticipated from liquid-liquid extraction data. This is also the case for a resin employing a related macrocyclic extractant, calix[4]arene-bis-(t-octylbenzocrown-6)("BobCalix), prepared and partly characterized in an effort to overcome certain limitations of the BC6B-based material. Despite this, the resin is shown to be well suited to the isolation of radiocesium from acidic solution for subsequent determination or for the removal of cesium intereference in the quantitation of other radionuclides.