Male Wistar rats were given 0.5% lead acetate and natrium acetate equimolar to 2% lead acetate for 3 months, 1 and 2% lead acetate for 2 months. Noradrenaline (NA) in hypothalamus and striatum corticosterone, thyroxine and 3,5,3'-triiodothyronine in serum and catecholamines (CA) in adrenals were determined at one month's interval. Results were accomplished by body and organ weights. All the changes depend on lead exposure level and time of exposure. At the three doses, lead exposure produced a significant decrease of NA in hypothalamus and striatum, increase of CA in adrenals and increase of kidney weight. Significant changes of all hormones, liver, spleen and kidney weight were observed in rats given 2% lead acetate. The stress effects of acetate was excluded by the lack of biochemical, organ or body weight effects of sodium acetate. Our results suggest a nonspecific stress reaction in rats activating hypothalamo-pituitary-thyroid-adrenal axis.