Aim-To examine the relationship between blood pressure decline and dementia risk. Methods-A community-based dementia-free cohort (n=947, 75+ years) was followed to detect dementia. Data were analyzed with Cox models. Results-Blood pressure markedly decreased before dementia diagnosis and continued to decline thereafter. Diastolic pressure decline was not predictive of dementia. Systolic pressure decline ⩾15 mm Hg was associated with an increased risk of dementia among people with baseline systolic pressure <160 mm Hg. Conclusions-Blood pressure decreases from the preclinical phase of dementia. A greater decline in systolic pressure is associated with dementia risk in selective subgroups of aging population.