Polychlorinated naphthalene (PCN) and polychlorinated biphenyl (PCB) congeners were measured in whole body and fillet of fishes collected from Michigan waters, including the Great Lakes, during 1996−1997. PCNs were found in all the fishes analyzed including those from Siskiwit Lake, a remote lake located near the southern shoreline of Isle Royale National Park in Lake Superior. Concentrations of total PCNs in fishes ranged from 19 to 31 400 pg/g, wet wt, and varied depending on sampling location and species. Fishes from the Detroit River contained the greatest concentrations of both PCNs and PCBs. Concentrations of total PCNs in fishes from Michigan waters were significantly correlated with the concentrations of PCBs. As with total PCN concentrations, the profiles of PCN isomer/congener distribution in fishes varied among sampling locations and species. Fishes from the Detroit River contained PCN profile similar to that of Halowax 1014, whereas those from Siskiwit Lake and Lake Superior contained greater ...