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Polybrominated diphenyl ethers (PBDEs) and hydroxylated PBDEs (OH-PBDEs) were determined in plasma of free-ranging bottlenose dolphins (Tursiops truncatus) from Charleston (CHS), South Carolina, and the Indian River Lagoon (IRL), Florida, USA. Significantly lower sums (∑) of PBDE concentrations (sum of 12 congeners) were found in animals from the IRL (arithmetic mean, 5.45 ± 4.63 ng/g wet wt) compared with those from CHS (30 ± 40 ng/g wet wt). Brominated diphenyl ether (BDE)- 47 was the predominant PBDE in dolphins from the IRL (50% of the ∑PBDEs) and CHS (58%). The ∑PBDE concentrations in plasma of dolphins were negatively correlated with age at both locations. Fifteen and sixteen individual OH-PBDE congeners could be quantified in plasma of dolphins from IRL and CHS, respectively. Similar to ∑PBDE, mean ∑OH-PBDE concentrations were significantly higher in plasma of dolphins at CHS (1,150 ± 708 pg/g wet wt)compared with those at IRL (624 ± 393 pg/g wet wt). The predominant congener at both locations was 6-OH-PBDE-47 (IRL, 384 ± 319 pg/g wet wt; CHS, 541 ± 344 pg/g wet wt), representing 61.5% of total ∑OH-PBDE at IRL and 47.0% at CHS. Concentrations of ∑OH-PBDEs were weakly negatively correlated with age in dolphins from both locations (p < 0.05; IRL, r² = 0.048; CHS, r² = 0.021). In addition to the OH-PBDE congeners identified with technical standards, eight and four unidentified OH-PBDEs were detected and quantified, respectively, in animals from CHS (sum of unidentified OH-PBDEs = 1.35 ± 0.90 pg/g wet wt) and IRL (0.73 ± 0.40 pgig wet wt). Results of the present study suggest that, unlike OH-PCBs, OH-PBDEs in bottlenose dolphins are minor products in plasma relative to ∑PBDEs and a significant proportion may be a consequence of the dietary uptake of naturally produced methoxylated- and OH-PBDEs. [ABSTRACT FROM AUTHOR]