Ambulatory blood pressure monitoring (ABPM) offers advantages over clinic blood pressure measurement. Supporting the arm at the level of the right atrium has long been standard in clinic blood pressure measurement. In contrast, there is no consensus regarding arm position in the guidelines addressing ABPM. Research studies have used a variety of arm positions during ABPM. Discussed in this review are the merits of ABPM and a review of the several arm positions recommended in ABPM guidelines, suggested by cuff manufacturers, and used in research studies. To address this lack of standardization, a rationale for a clinically reasonable arm position during ABPM is offered. Specifically, the authors recommend advising the patient to keep the arm still and relaxed straight down at the side of the body when the cuff is going to inflate, when safe to do so.