It has been shown by others that offspring of mothers who had been exposed to dioxins and polychlorinated biphenyls (PCBs) during pregnancy have elevated plasma levels of thyroid-stimulating hormone (TSH) for at least 3 months after birth and reduced plasma levels of free and total thyroxine during the second week after birth. As elevated levels of dioxins and PCB s can thus alter thyroid hormone status, the relation between the levels of some polychlorinated organic compounds in the blood lipids and growth and thyroid hormone status was studied in 12 hospitalized schoolchildren from the Aral Sea region known to have high exposure to such compounds. Their level of PCBs was two to four times higher than in healthy Stockholm children. Their height was found to be lower than in healthy Swedish children of the same age mean (SDS -0.52) and the body mass index (BMI) was inversely correlated to the total concentrations of PCBs and dichlorodiphenyltrichloroethane (DDT) and its metabolite dichlorophenyldichloroethylene (DDE) in the blood lipids. As the levels of insulin-like growth factor- were reduced to the same extent as the BMI it seems likely that PCBs and DDT cause malnutrition as a result of malabsorption. None of the children had any impairment of thyroid function, as revealed by the plasma levels of TSH and thyroxine. Although the concentrations of beta-hexachlorocyclohexane (beta-HCH) and DDE were extremely high in some of the children there was no relation between thyroid hormone status and the blood lipid levels of PCBs, hexachlorocyclohexane and DDT. However, the concentration of dioxins was not analysed.