Summary: The use of mechanism-specific bioassays has a large potential in many areas, including toxicity characterisation of contaminated soil. Also during different types of remediation techniques of soil, bioassays serve a useful purpose, since they may shed some light on changes in bioactivity of soil pollutants before, during and after a specific remediation process. Bioremediation of polluted soil is now an established technique and efficient bioremediation techniques exist for the removal of polycyclic aromatic hydrocarbons (PAHs). Rowever, more needs to be elucidated about formation of more toxic metabolites during such remediations. Many PAHs are also AhR agonists, which makes bioassays for dioxin-like compounds useful tools in this context. One ofthe most common bioassays is the DR-CALUX, which has been adapted in our lab for the study of dioxin-like compounds in soil. In this project the DR-CALUX dioxin bioassay was used to study dioxin-like toxicity before, during and after bioremediation of PAH-contaminated soil in Sweden.