Structure of a mutagenic compound (Me-IQ) isolatedfrom broiled fish was determined to be 2-amino-3,4-dimethylimidazo[4,5-f]quinoline based on the mass-, UV- and 1H-NMR-spectra and chemical synthesis. Me-IQ showed strong mutagenic activity towards Salmonella typhimurium TA98 in the presence of S-9 mix.