Our 4th Advanced Toxicology Course was focused on “Genotoxicity & Mutagenicity testing: a brief overview of the main tests, pitfalls and regulatory”. The course was a joined initiative of Beltox and BEMS and was hosted at the Elewijt Center on October 4th. We were glad to welcome almost 30 participants for this rather specific course, with participants of all regions of Belgium and a few from neighboring countries. The course was built from the theory to practice, starting with background and mechanisms discussed in detail by Ilse Decordier, the testing guidelines by Ilse Koijen & Bas-Jan van der Leede to more regulatory aspects by Sonja Beken and finally Philippe Vanparys discussed false positives and testing strategies. The course was completed with an intensive practical section in which data (observations) from tests were distributed to the participants together with some questions to solve. This exercise was very well structured and upon questions additional data was released by the facilitators (Ilse Koijen & Bas-Jan van der Leede). The day was concluded with an interactive discussion on the interpretation of the data.