Abstract: The uptake of 137-Cs and 90-Sr on to synthetic zeolite A has been studied. The use of a combined barium exchange followed by a relatively mild heat treatment has been shown to fix the isotopes within a collapsed zeolite structure. Leaching experiments using deionized and simulated sea and pond waters were carried out on zeolite compacts and zeolite/cement composites. They demonstrated the effectiveness of the calcination and cement containment. Some comments on the interpretation of leach test data are made.