Abstract—Studies of the association of high blood pressure (BP) with dementia are not consistent. Understanding long-term trajectories in blood pressure of those who do and do not develop dementia can help clarify the issue. The Honolulu Heart Program/Honolulu-Asia Aging Study followed a cohort of Japanese American men for an average of 32 years, with systolic BP (SBP) and diastolic BP (DBP) measured at 6 examinations and dementia assessed at the final 3. In an analysis of 1890 men who completed all 6 of the exams, 112 diagnosed with incident dementia at examination 6 were compared with the 1778 survivors without dementia. Trajectories in SBP and DBP up to and including the sixth examination were estimated with a repeated-measures analysis using 3 splines. From midlife to late life, men who went on to develop dementia had an additional age-adjusted increase in SBP of 0.26 mm Hg (95% CI: 0.01 to 0.51 mm Hg) per year compared with survivors without dementia. Over the late-life examinations, this group had an additional age-adjusted decline in SBP of 1.36 mm Hg (95% CI: 0.64 to 2.07 mm Hg) per year. These associations were strongest for vascular dementia and were reduced substantially in men who were previously taking antihypertensive medication. Similar changes in diastolic BP were observed, but only for vascular dementia, and the findings were not modified by antihypertensive treatment. Over a 32-year period, compared with men who did not, those who did develop dementia had a greater increase, followed by a greater decrease, in SBP. Both of these trends are modified by antihypertensive therapy.