Recently, there has been an increase in studies focusing on an emerging class of organic contaminants, hydroxylated PCBs (OH-PCBs) and chlorinated phenolic compounds (CPCs) in the environment, particularly in northern regions of Europe and Canada. Since information for fish from the Great Lakes are scarce, we determined the blood plasma concentrations of OH-PCB congeners, pentachlorophenol (PCP), 2,3,4,5-tetrachlorophenol (TCP), and 4-hydroxyheptachlorostyrene (4-OH-HpCS) for lake trout (Savelinus namaycush) collected from two of the Great Lakes, Lake Ontario and Lake Superior, and two regional lakes, Lake Champlain and Lake Opeongo. PCP was the dominant CPC in lake trout (105-658 pg/g of plasma). Detectable concentrations of 2,3,4,5-TCP and 4-OH-HpCS were found in all lake trout (2.6-101 and 0.4-27 pg/g, respectively). Highest concentrations were found in trout from Lake Ontario and Lake Superior. Sixteen OH-PCBs were quantified, with 4-OH-CB187 having the highest concentration in all samples (10-173 pg/g of plasma). Unexpectedly, highly chlorinated OH-PCBs such as 4'-OH-CB199 (mean 21.4 and 74.4 pg/g), 4,4'-diOH-CB202 (18.3 and 27.7 pg/g), and 4'-OH-CB208 (24.5 and 34.7 pg/g) were found in lake trout from Lake Ontario and Lake Superior, respectively. Future studies to delineate the sources and impacts of CPCs in the Great Lakes catchment are needed.