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. 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. 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, rs = -0.29, P < 0.001). This association remained after age adjustment. 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.