In-situ immobilization of metals, with the aid of metal immobilized soil additives, is a potential strategy for remediation of metal-contaminated soils. Various mechanisms such as sorption, and (co) precipitation reactions, induced by the addition of an additive to the ground, can cause a reduction of the bioavailability of metal and so are the risks associated with contamination. Mainly for large-scale diffusion of impurities, as in the Belgian (and Dutch) Kempen, this technique seems, by its relatively low cost and little significant impact on the environment, an attractive option. Plenty of different products have been investigated as potential soil additives in this context, but to compare the efficiency of different soil additives through the numerous studies on metalimmobilization - with a view to the selection of the 'best' additive or a ranking by increasing immobilizationcapacity - is by no means obvious. This difficulty is mainly due to the fact that often different evaluation methods have been used by several research groups, but in addition the action of soil additives is also dependent on soil. A thorough literature study therefore provides no ready solution for the 700 square kilometers contaminated soils in the Kempen. The project is a risk-based soil in the Kempen, based on the reduction of the mobility and bioavailability of heavy metals in the soil. The project includes two components: the development of an optimized and standardized evaluation protocol with a physio chemical, biological and ecotoxicological environmental aspect, and suitability analysis of several potential metal immobilized soil additives and their commercialization. Results from this study are finally tested against the principles of risk-based remediation in close consultation with OVAM.