The Ames MPF 98/100 AQUA is designed to detect the mutagenic potential of non-concentrated water samples. The assay allows to use 18.5 times more sample volume than with the conventional Ames MPF 98/100 for testing of chemical compounds thanks to a 10-fold concentrated Exposure Medium. The assay uses S. typhimurium TA98 and TA100 for the measurement of base-pair substitutions and frameshift mutations. The assay may be used for the testing of sterile aqueous solutions, such as fresh water, waste water, aqueous extracts and leachates, aqueous solutions of chemicals and chemical mixtures.