A metabolite of 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) was incorrectly characterized in this paper. The metabolite was thought to be an acetyl conjugate of the 5-hydroxyl-ated derivative of MeIQx. This assignment is incorrect. The correct assignment is a sulfate conjugate of 5-hydroxy-MeIQx, 2-amino-3,8-dimethylirnidazo[4,5-f]quinoxaUn-5-yl-sulfate. This conclusion is based upon repurified sample analyzed by 1H NMR and 13C NMR, enzyme hydrolysis assays, IR spectro-scopy and FAB/MS (accurate mass measurement).