1. The changes in blood glucose, plasma noradrenaline and plasma renin activity were measured in 11 normal subjects and in six tetraplegic subjects with a transection of the cervical spinal cord (preganglionic sympathectomy), in response to acute insulin-induced hypoglycaemia (0.15 unit/kg).
2. After hypoglycaemia, a pronounced rise in plasma noradrenaline was observed in the normal subjects but was absent in the tetraplegic group; plasma renin activity increased markedly in both groups.
3. It is concluded that the stimulation of renin release in response to hypoglycaemia can occur independently of any activation of the sympatho-adrenal system.