Recent studies have shown that there is a relationship between an alteration of central neurotransmitters and the modification of some biohumoral parameters in Alzheimer's Disease (AD). In this study the authors evaluated, after metoclopramide (MTC) stimulation, the concentration curve of vasopressin (AVP), prolactin (PRL) and growth hormone (HGH) in the plasma of 34 subjects (20 males and 14 females, mean age 70.5+/-6.9 years; 17 were AD patients, the others constituted the control group). MTC increased AVP serum concentration in healthy (P <0.001), but not in AD patients. This result seemed to be due to the lack of 'procholinergic' action of the drug in the AD patients probably due to an alteration in their cholinergic pathways. The PRL response to MTC was reduced only in the AD female group (P <0.005), suggesting an alteration in dopaminergic control. Lastly, the HGH response in AD did not differ in the two groups, neither in basal conditions, nor after MTC stimulation. The absence of HGH response both in AD and in healthy subjects, demonstrated the ineffectiveness of MTC stimulation. We can conclude that AVP and PRL responses to MTC stimulation efficiently separated the two groups (AD and controls); the former test showing a higher discriminant power than the latter.