Since Riva-Rocci and Korotkoff gave us the technique of conventional blood pressure (BP) measurement over a century ago, we have landed men on the moon, encircled Mars, invented the automobile and airplane, and, most importantly, revolutionized the technology of science with the microchip. Why, we might ask, has medicine ignored scientific evidence for so long so as to perpetuate a grossly inaccurate measurement technique in both clinical practice and hypertension research? The same sentiment has been expressed by Floras: “As a society, we are willing to contemplate widespread genomic or proteomic subject characterization in pursuit of the concept of ‘individualized medicine.’ By contrast, blood pressure measurement is one of the few areas of medical practice where patients in the twenty-first century are assessed almost universally using a methodology developed in the nineteenth.”1 It is generally accepted that traditional clinic or office BP measurement (OBPM) is limited in the amount of information that it can provide for the adequate management of hypertension and that contemporary practice must turn to out-of-office measurement to obtain additional information to guide the diagnosis and management of hypertension. The methods available for out-of-office measurement are ambulatory BP measurement (ABPM) and self- BP measurement (SBPM). The purpose of this review is not to restate the criteria for measurement by these techniques, which have been described in detail previously,2,3 but rather to present evidence to support the opinion that ABPM should be available to all primary care physicians who are responsible for the management of the majority of patients with hypertension. Hypertension is a major global risk for cardiovascular morbidity and mortality,4 and the World Health Organization, aware of the paucity of BP measurement devices in low-resource countries is piloting studies to redress this serious deficiency.5 Clearly, therefore, the out-of-office techniques addressed in this …