Organohalogen chemicals of emerging concern (CECs) have attracted much attention during the past decade and are of special importance for the Great Lakes of North America, which are together the largest surface freshwater resource on the earth. In this paper we review and summarize detection and levels of legacy contaminants in Great Lakes fish, lessons learned from legacy contaminants in advancing the analytical detection of CECs, progress and challenges in measuring CECs, and levels of CECs in Great Lakes fish reported to date. The CECs considered include chlorinated paraffins, polychlorinated naphthalenes and other chlorinated aromatics, halogenated flame retardants, and perfluorinated compounds.