Aluminium is present in senile plaques and in neurofibrillary tangle-bearing neurones in brains of cases of Alzheimer’s disease. Evidence linking aluminium absorption to calcium metabolism prompted a case-control study of physiological markers of calcium homeostasis in patients with Alzheimer’s disease. Mean plasma 25-hydroxyvitamin D concentration was lower in cases than in controls but no difference in median parathyroid hormone concentrations or other evidence of altered calcium metabolism was found. The difference in 25-hydroxyvitamin D concentrations may be secondary to differences in exposure to sunli