Water immersion up to the neck (WI) results in a central hypervolemia; the increased atrial pressure, evoked by this maneuver, stimulates low pressure receptors (LPR) which exert tonic inhibition on sympathetic activity and suppresses both the renin (PRA)-aldosterone (PA) system and the ACTH-cortisol axis in normal man. In hemodialyzed patients (HP), in whom autonomic neuropathy has been frequently found, PRA and ACTH were not suppressed during WI while plasma cortisol and PA were reduced. Other modulators, like dopamine, are supposed to be involved in regulating cortisol and PA levels in HP.