STUDY OBJECTIVE:The aim was to examine whether a high intake of aluminium containing antacids is a risk for Alzheimer's disease. DESIGN:The mortality from dementia (1970-87), coded from death certificates as underlying or contributory cause of death, was compared with national rates in a cohort of patients who had surgery for gastroduodenal ulcer disease between 1911 and 1978. SETTING:Patient data were obtained from patient records from major hospitals in western Norway. PARTICIPANTS:4179 patients were identified who met the study criteria, which included having had a documented stomach operation, having a reliably identifiable personal number, and being alive on Jan 1, 1970. MEASUREMENTS AND MAIN RESULTS:The standardised mortality ratio for dementia was 1.10 (95% CI 0.85-1.40, n = 64) for all patients, while for patients operated on in the period 1967-78 it was 1.25 (95% CI 0.66-2.13, n = 13). CONCLUSIONS:As the majority of patients operated on after 1963 have probably been heavy consumers of aluminium containing antacids, the study provides meager evidence that a high intake of aluminium is an important risk factor for Alzheimer's disease, the major cause of dementia. However, the possibility of a raised mortality from Alzheimer's disease cannot be ruled out due to probable misclassification both in diagnosis and exposure. In addition, the observation period may have been too short to detect an effect since the latent period for Alzheimer's disease may be very long.