Alzheimer's disease (AD) has been linked to genetic defects on chromosome 21 in some families, but most elderly cases appear to be sporadic and may, at least in part, involve environmental risk factors. Several lines of evidence suggest that aluminium may be involved in the aetiology of AD. However, despite universal exposure to aluminium in the diet, only some people develop the disease. We have developed a test of aluminium absorption using an aluminium citrate drink, to examine the hypothesis that sufferers from AD show increased aluminium absorption. In a younger group of AD patients aluminium absorption was significantly raised compared with age-matched controls. Aluminium absorption increased with age in the control group but was not significantly raised in older AD patients when compared with age-matched controls.