This study reports hepatic concentrations and distribution patterns of select metals, organochlorine pesticides (OCs), polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in 180 male river otters (Lontra canadensis) collected from Oregon and Washington, 1994-1999. Seven regional locations of western Oregon and Washington were delineated based on associations with major population centers, industry or agriculture. Cadmium (Cd) was not found above 0.5 ??g g-1, dry weight (dw) in juveniles, but increased with age in adults though concentrations were generally low (nd-1.18 ??g g-1, dw). Regional geometric means for total mercury (THg) ranged from 3.63 to 8.05 ??g g-1, dw in juveniles and 3.46-2.6 ??g g-1 (dw) in adults. The highest THg concentration was 148 ??g g-1, dw from an apparently healthy adult male from the Olympic Peninsula of Washington. Although THg increased with age in adult otters, the occurrence of the more toxic form methylmercury (MeHg) was not evaluated. Mean OC and PCB concentrations reported in this study declined dramatically from those reported in 1978-1979 from the lower Columbia River. Organochlorine pesticide and metabolite means for both juvenile and adult river otter males were all below 100 ??g kg-1, wet weight (ww), with only DDE, DDD and HCB having individual concentrations exceeding 500 ??g kg-1, ww. Mean ??PCB concentrations in both juvenile and adult male otters were below 1 ??g g-1 for all regional locations. Mean juvenile and adult concentrations of non-ortho substituted PCBs, PCDDs and PCDFs were in the low ng kg-1 for all locations studied. ?? Springer Science+Business Media B.V. 2007.