The concentration of copper in the rat brain hypothalamus showed a dose-dependent increase with the administration of copper ions. With doses larger than 3 mg/kg the copper content was higher when measured 30 min after administration of the metal and was depleted to near control values after 6 h. Copper ions in doses of 3, 5 and 10 mg/kg increased dopamine and decreased noradrenaline contents of the hypothalamus in a non-linear fashion. Peak hypothalamic dopamine content was found 30 min after injection of copper (5 mg/kg) which returned to normal levels after 6 h. Ascorbic acid (500 mg/kg) administration prevented the copper-induced dopamine increase in the brain. Ascorbic acid also caused the copper content of the tissue to decrease in both normal and copper-receiving rats. However, the effect of the vitamin on catecholamine content of the hypothalamus was opposite to that of copper ions, i.e. it caused noradrenaline to increase and dopamine to decrease in comparison to control values. The results suggest that ascorbic acid may reduce the effects of excessive copper deposition in the brain hypothalamus.