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, U.S.A. Significantly lower sums (sigma) 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 sigma PBDEs) and CHS (58%). The sigma 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 sigma PBDE, mean sigma OH-PBDE concentrations were significantly higher in plasma of dolphins at CHS (1150 +/- 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 sigma OH-PBDE at IRL and 47.0% at CHS. Concentrations of sigma 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 pg/g wet wt). Results of the present study suggest that, unlike OH-PCBs, OH-PBDEs in bottlenose dolphins are minor products in plasma relative to sigma PBDEs and a significant proportion may be a consequence of the dietary uptake of naturally produced methoxylated- and OH-PBDEs.