The Salmonella/microsome assay is the most used mutagenicity test both for evaluation of chemicals and environmental samples. There are several versions of protocols available in the literature. The microsuspension version of this assay is performed with conventional petri dishes and uses 10 times less sample and S9 mixture. The objective of this study was to miniaturize of the microsuspension Salmonella/microsome assay using agar microplates under the concept of the 3R.