AbstractVasomotor reactivity has been evaluated in rats exposed perinatally and postnatally to thallium sulphate (1 mg/dl in their drinking water ad libitum).Prenatal and postnatal exposure to thallium did not modify the values of the systolic arterial blood pressure on the 30th and 60th day in pups of normotensive and DOCA‐hypertensive rats. The hypertensive responses induced by endosinusal carotid hypotension and by 1‐noradrenaline in pups of normotensive and DOCA‐hypertensive rats, exposed or not exposed to thallium sulphate, were more intensive on the 60th than on the 30th day. Similar effects were observed for the hypotensive responses induced by 1‐isoprenaline and acetylcholine. Prenatal exposure to thallium did not modify hypertensive responses induced by endosinusal carotid hypotension on the 30th and 60th days, but it caused a decrease of hypertensive responses induced by 1‐noradrenaline on the 30th and 60th days and hypotensive responses induced by 1‐isoprenaline and acetylcholine exclusively on the 60th day.Postnatal exposure to thallium did not modify hypertensive responses induced by endosinusal carotid hypotension and hypotensive responses induced by acetylcholine, but it caused a decrease of hypertensive responses induced by 1‐noradrenaline on the 30th and 60th days in pups of normotensive rats and exclusively on the 60th day in pups of DOCA‐hypertensive rats. Moreover, postnatal exposure to thallium caused a decrease of the hypotensive response induced by 1‐isoprenaline exclusively on the 60th day.Our findings show that prenatal and postnatal exposure to thallium sulphate modifies the rat's developing vascular autonomic nervous system with a reduction of the α, β‐adrenergic and muscarinic