The influence of different parameters on the leaching of Cesium from cemented BWR evaporator concentrates (Sulphates) was tested. In particular the variation of the following parameters was evaluated: temperature, initial concentration of the tracer, renewal and chemical composition of the leachant, size of the specimen. In a further series of tests the following effects on leaching were also taken into account: volume of leachant, addition to the mix of an air entraining agent, shorter curing times (3 days instead of 28 days), different way of carrying out the test (static, instead of dynamic conditions). Demonstration is given that only a few parameters, like temperature and chemical composition of the leachant, have some effects on leaching. A strong influence however is caused by the way used to prepare the samples, which, in general, can strongly modify the final properties of cemented waste materials.