<h3>Objective:</h3> To evaluate whether seated blood pressure (BP) could predict symptomatic hypotension in Down syndrome (DS) individuals with Alzheimer disease (AD) <h3>Background:</h3> Hypotension in DS is well-described and attributed to brain degeneration ( <b><i>J Ment Defic Res</i></b> 1979; <b><i>J Clin Psychopharmacol</i></b> 1989). Subsequently, a link to AD in DS was postulated (<b><i>Hypertension</i></b> 1996). <h3>Design/Methods:</h3> We reviewed all available out-patient seated BP values of 18 DS individuals with AD (9 female; mean age, 49.8 years) who presented from their group homes to a neurologist as a consecutive out-patient series from January 2000 to January 2017 because of dizziness or syncope attributed to hypotension. We compared BP prior to the initial symptom with BP post-treatment. A control group consisted of 19 DS individuals with AD (9 female; mean age, 51.4 years) without dizziness or syncope. <h3>Results:</h3> An average of 4.1 BP measurements were available pre-treatment, 8.1 post-treatment, and 5.0 in the control group. Mean BP in the treatment group was 110/67 prior to diagnosis of hypotension. No trend in BP was observed in the period prior to diagnosis of hypotension (R<sup>2</sup> = 0.041 for systolic and 0.066 for diastolic). All symptomatic patients were treated (fludrocortisone, 7; midodrine, 7; both, 2; added salt, 1; adjustment of other medications, 1). All treated patients were symptomatically improved. Mean BP after treatment was 106/65, not significantly changed from pre-treatment (p = 0.051 for systolic and 0.172 for diastolic). The treatment and control groups did not differ in gender or age. Mean BP in the control group was 103/64, not significantly different from the pre-treatment group (p = 0.143 for systolic and 0.140 for diastolic). <h3>Conclusions:</h3> Although hypotension is common in the DS population with AD, seated BP measurements did not help predict which individuals would become symptomatic. Treatment was effective even without significant demonstrable change in BP values. <b>Study Supported by:</b> NA <b>Disclosure:</b> Dr. Huttler has nothing to disclose. Dr. Shauly-Aharonov, PhD has nothing to disclose. Dr. Jeret has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Eli Lilly.