A study was conducted to determine whether changes in thyroid and vitamin A dynamics were induced in ranch mink exposed to environmentally relevant concentrations of polyhalogenated aromatic hydrocarbons. Adult female mink were fed diets that contained 0% (control), 10%, 20%, or 30% wild carp (Cyprinus carpio) collected from the Saginaw River, Michigan, USA. Total polychlorinated biphenyls concentrations were 0.03, 0.83, 1.05, and 1.69 mg/kg feed, respectively; the 2,3,7,8-tetrachlorodibenzo-p-diozin toxic equivalents were 3.4, 27.9, 47.6, and 73.2 ng/kg, respectively. Diets were fed 3 weeks prior to breeding and throughout gestation and lactation. When the kits were weaned at 6 weeks of age, they were continued on their respective diets until 27 weeks of age. Plasma thyroid hormone concentrations, thyroid gland activity and structure, and vitamin A dynamics were assessed in young mink at 6 and 27 weeks of age. Plasma total T4 and free T4 in 6-week-old female and male kits fed the 10% carp diet were significantly higher than those of controls, while kits fed the 20% and 30% carp diet had nonsignificant decreases relative to the control mink. Plasma total T3 concentrations in 27-week-old juvenile males fed the 30% carp diet were significantly lower than those in individuals fed the 10% carp diet. No overt thyroid toxicity was apparent as thyroid weight, activity, and structure in kits and juveniles of both sexes were similar among diet groups. Plasma retinol and total ester concentrations in both kits and juveniles were reduced in mink fed the 30% carp diet relative to controls. The ratio of retinol to retinyl palmitate in livers of juveniles fed the 30% carp diet was two times higher than that in control mink. Significant reductions in kidney retinol and fatty acyl retinyl esters were observed in kits and juveniles fed the 30% carp diet relative to control values.