As a precautionary measure, the re-use (or landfill) of waste requires an environmental assessment of its potential impact. This assessment is usually made by simulating the emission of pollutants with a predictive model based on laboratory tests (standardised batch leaching tests, up-flow percolation tests, acid neutralisation capacity tests [CEN, Characterisation of Waste - Leaching - Compliance Test for Leaching of Granular Waste Materials and Sludges, European Committee for Standardisation (ECS), Brussels, 2002 [1]; CEN, prCEN/TS 14405 Characterisation of Waste - Leaching Behaviour Tests - Up-flow Percolation Test (under specified conditions), ECS, Brussels, 2002 [21; CEN, prCEN/TS 14429 Characterisation of Waste - Leaching Behaviour Test - Influence of pH on Leaching with Initial Acidibase Addition, ECS, Brussels, 2003 [3]]. These tests a-re performed with simpler conditions than those occurring in the scenario of re-use (saturated media, permanent inflow...). In order to evaluate the relevance of these tests to be considered as a reference for predictive model, the purpose of this work is to determine how the intermittent hydrodynamic flow influences the pollutants release of unsaturated waste. As a result, we could estimate whether this parameter should be introduced in the model. (c) 2006 Elsevier B.V. All rights reserved.