1. Rats genetically sensitive to salt-induced hypertension showed higher levels of plasma noradrenaline and adrenaline than rats genetically resistant to hypertension. 2. The hypertension-sensitive rats had higher hypothalamic noradrenaline and lower adrenaline than resistant rats. 3. In response to a high salt diet brain-stem noradrenaline increased in sensitive rats and resistant rats exhibited a decrease on the same diet.