The aim of this study was to determine the effect of transportation on the behaviour and stress responses of the sympatho-adrenal and hypothalamo-pituitary-adrenal systems in mares and their foals by measuring the peripheral plasma concentrations of adrenaline, noradrenaline and cortisol. Control blood samples were taken from mares and their foals (n=5 pairs) on day 8 after parturition to establish whether blood sampling caused any changes in adrenaline, noradrenaline or cortisol concentrations in blood plasma. The experiment was conducted during foal oestrus (on day 9 after parturition). Adrenaline and noradrenaline concentrations increased in the blood plasma of mares after only 10 min transportation and the increased concentrations were maintained until 30 min after transportation. The adrenaline and noradrenaline concentrations in foal blood plasma increased after 10 min transportation and decreased rapidly to basal concentrations. Cortisol concentrations in the blood plasma of mares reached a peak after 60 min transportation. Peak cortisol concentrations in foal blood plasma were attained after transport was completed. The results of the present study indicate that transportation during foal oestrus is a stronger stress-causing factor for mares than for their foals.