Short-term stress exposure is associated with activation of the hypothalamic-pituitary-adrenal (HPA) axis and a consequent rise in blood glucocorticoids and catecholamines, from the adrenal cortex and medulla, respectively. The HPA axis is a potential target for some persistent organic pollutants, among which polychlorinated biphenyls (PCB) were found to be modulators of the mammalian endocrine system. PCB are distributed globally in the environment, in food chains, and are transferred to the fetuses of pregnant animals and via mother's milk to suckling offspring. In the present study it was postulated that intrauterine and lactational exposure to either of two single congeners of PCB (PCB 153 and PCB 126, respectively) might affect basal cortisol concentrations, and also the cortisol response to short-term stress in adulthood. Thus, pregnant goats were orally exposed to one of these PCB congeners from d 60 of gestation until delivery, and their offspring studied. Low-dose exposure to PCB 153 and PCB 126 resulted in significantly lower mean basal cortisol concentrations in goat offspring during certain periods of pubertal development and their first breeding season. Male goat kids exposed to either PCB congener showed a greater and more prolonged rise in plasma cortisol levels than controls when animals were subjected to mild stress at 9 mo of age using frequent blood sampling. Neither the basal maternal cortisol plasma level nor goat kid adrenal masses were affected by PCB exposure.