On September 11, 2014 the European Food Safety Authority (EFSA) will hold a scientific colloquium on the harmonization of human and ecological risk assessment of combined exposure to multiple chemicals in Edinburgh, UK. The meeting shall provide a forum for scientific debate on i) mechanistic models for hazard assessment, ii) harmonization of methods for combined exposure assessment, iii) the use of OMICs and in silico methods for risk assessment, and iv) the application of science-based uncertainty factors and approaches for risk characterization using mechanistic approaches. EFSA invites risk assessors, scientists and policymakers to discuss the 4 topics in discussion groups. The meeting will be concluded with a final plenary session where conclusions and, if possible, recommendations shall be formulated. The meeting registration on the EFSA webpage is open until all available spots are filled.