Objectives: There is a concern that persistent organohalogen toxicants, such as polychlorinated biphenyls (PCBs), might display endocrine-disrupting effects in exposed populations. In this study the correlations between PCBs and thyrotropin (TSH) and thyroid hormone concentrations in plasma were assessed in adult women. Methods: The study group consisted of 182 fishermen's wives from the Swedish east coast, with a median age of 42 years (range 23–62) and a median current consumption of contaminated fatty fish from the Baltic Sea of two meals per month (range 0–12). TSH, free (FT₃) and total (TT₃) triiodothyronine and free (FT₄) and total (TT₄) thyroxin in plasma were analyzed by immunofluorometric assays, and 2,2′,4,4′,5,5′-hexachlorobiphenyl (CB-153) in plasma was analyzed by gas chromatography with electron capture detection. Twenty other PCB and two hydroxy-PCB congeners were analyzed in subgroups of the women. Plasma lipid analyses were performed with enzymatic techniques. Results: The CB-153 concentration in plasma (range 16–776 ng/g lipid) was negatively correlated with the TT₃ concentrations (range 1.0–3.0 nmol/l, r_s=−0.29, P < 0.001). This association remained after age adjustment. Conclusions: The present study gives some support for the notion that dietary exposure to persistent organochlorine compounds (POCs) might weakly affect peripheral thyroid hormone concentrations in adult women.